September 10, 2022

From a distance, this sparse patch of sunflowers looks nondescript. You’d have no idea that it’s the stage for a gripping insect drama. But here we are, five adults, completely engrossed in this miniature world in front of our eyes. We’ve already spotted a golden paper wasp, two magnificently hairy velvet ants, and a spined assassin bug. And we keep spotting more creatures, each of them exciting. It’s a scramble to keep track of them all and get photos.

We’re about 18 miles southeast of Missoula today, close to where Rock Creek flows into the Clark Fork River. We’re standing in a rocky wetland area on the Rock Creek Confluence property, a Five Valleys Land Trust site that offers public day use and an interpretive trail. Prior to 2016, this wetland was a pond, kept full with irrigation water. Since then, Five Valleys Land Trust has returned their water right to in-stream flow, supporting bull trout, cutthroat trout, and other inhabitants of Rock Creek. And the once-full pond has become a shallow wetland under restoration. Now the water levels fluctuate with the groundwater. Volunteers have helped plant a variety of native plants, and others are establishing on their own. A deer fence currently surrounds the area, limiting attention from deer while the plants develop.

Getting started with the insects

As part of the restoration project, we’re here today to document a few of the most visible insects we can find in this habitat. Glenn Marangelo of the Missoula Butterfly House is leading this field day. By the time I arrive (20 minutes late), there are three other naturalists helping with the search: Kelly Dix, Kristi DuBois, and Jenny Lundberg. 

We’re hovering excitedly around the sunflower patch, in the dry cobbles above the wetland. A golden paper wasp (Polistes aurifer) is still perching quietly on a sunflower stem. It’s exciting to see this native species here – at least in my observations around Helena, this wasp seems uncommon compared to the European paper wasp (Polistes dominula), a non-native relative that has become ubiquitous.

“Is that another assassin bug up above him, hanging from that flowerhead?” asks Jenny. 

There it is, an outlandish, long-legged tan bug with a narrow head and neck. 

“Really!? Oh, that’s cool!” says Glenn, every word full of excitement.

For all of their drab tan camouflage, assassin bugs (Sinea spp.) are vicious predators. They hunt any small or medium insects they can find, sucking the juices out of their hapless prey. And this is the second one we’ve seen here in these few minutes of looking. The other one dropped to the ground, where I was able to get photos of it.

Ambush bugs and velvet ants

We haven’t finished watching the assassin bug when I spot one of its more-colorful relatives trying to hide behind a flowerhead. This armored, rough-textured black and yellow creature is a jagged ambush bug (Phymata sp.). Remarkably camouflaged among yellow flowers, like goldenrods and sunflowers, these bugs prey on unwary flower visitors. But here, against the green bracts, this predator is obvious. It must realize how much it stands out, because soon it flies off, in search of a better hiding spot.

Just minutes before, we had spotted a velvet ant on the sunflowers. Wingless and antlike, but way fuzzier, we watched it crawl methodically along the plant, then drop to the ground when we disturbed it. Not ants at all, these unique wasps (family Mutillidae) are parasitoids that attack the young of certain other insects, especially ground-nesting bees and wasps. They seem rather uncommon, and it’s always a treat to see them. Don’t pick them up, though – some species can give a nasty sting when they’re attacked.

From forest to wetland

In the distance, we can hear the chipping of red crossbills from the mature ponderosa pine stand along the interpretive trail. A few minutes ago, the Clark’s nutcrackers were giving their nasal calls there, too. I arrived at the trailhead at the same time as Jenny. From there, it took us almost half an hour to walk the 1/3 mile from there to the wetland, distracted by the spiders, moths, and grasshoppers within the pine forest. From the invertebrates and the bird calls, it’s easy to tell: the community in the ponderosas is completely different from that of the wetland.

Here in the wetland, small flocks of migrating American pipits are landing to forage, giving their sharp “sip-it” calls. A killdeer is foraging in the mud. And right around us, we’re finding new insects so fast that Glenn is hard-pressed to both get photos and write everything down.

Webworm moths and ladybugs

The fall webworm moths (Hyphantria cunea) have completely denuded a small chokecherry, replacing the once-green leaves with a massive, silky web. We find one caterpillar still at home – the others have already moved on. The web also yields a couple of ladybugs. A convergent ladybug (Hippodamia convergens) has died here, though whether it was at the end of its life or got trapped into the webbing isn’t entirely clear. 

But near this ladybug we find one that’s still alive, a less-elongate creature with a conspicuous black line where the wing covers meet. It’s a nine-spot! This species (Coccinella novemnotata) is in decline – and even here in Montana, where people continue to spot them, they’re rather rare. When I found six of them in a sagebrush stand near Helena earlier this summer, they were vastly outnumbered by the 142 other ladybugs I counted. Nine-spots are always a special sight. After Kristi takes photos of it, we remove the nine-spot from the webbing. Before I can get any photos, it flies off.

We stop briefly by some clumps of white sagebrush (Artemisia ludoviciana) loaded with inconspicuous yellow flowers. Conspicuous or not, the honeybees have found them. Several dozen honeybees are getting lunch on these flowers, along with a couple of smaller flies.

Insects near the water’s edge

Out in the moister soil near the water’s edge, the striped ground crickets (Allonemobius fasciatus) are singing from their hiding places among the vegetation and the mud cracks. Meadowhawks (Sympetrum spp.), those red and black dragonflies, are in constant activity here, perching and making short flights. We spot at least five species: striped, black, band-winged, white-faced, and cherry-faced meadowhawks. A variety of lyre-tipped spreadwings (Lestes unguiculatus) are fluttering around us, too. 

Up close, the eyes of these damselflies are like blue ocean planets. With such prominent eyes, it’s no wonder damselflies and dragonflies are excellent hunters. It makes them hard to catch, too! I do manage to catch a striped meadowhawk (Sympetrum pallipes) for a closer look.

We’re almost ready for a lunch break, but as we’re walking back I notice a brilliant green beetle making its way among the damp gravels of the wetland. It’s a species I haven’t seen before, its legs deep amber and its wing covers coated with short, golden hairs. A closer look tells me that it’s a species of carabid (family Carabidae), a group of ground-dwelling beetles that hunt whatever insects they can catch.

Pygmy grasshoppers and meadowhawks

After our lunch break, we return to the search, making a loop around the other side of the wetland. A pygmy grasshopper leaps up from my path. It’s well-hidden against the mud. Smaller than my thumbnail, the top of its thorax is prolonged over its back into a slender point, a distinctive characteristic for this group (family Tetrigidae). These little grasshoppers eat mosses, algae, and decaying vegetation.

The meadowhawks are hard at work now, laying eggs. We stop to watch them, dozens of pairs, rising up and down in a quiet dance over a meadow of spikerush (Eleocharis sp.) ten yards from the water. They’re laying eggs here. When the water rises in the spring, the eggs will hatch. The aquatic larvae, voracious predators like the adults, will develop rapidly to bring forth the next late-summer spectacle, this hover-dance over the spikerush.

A giant water bug and a katydid

Now we’ve reached the edge of the water, and Glenn has spotted something he’s been looking for all day. It’s large, the size of a frog, rowing gracefully away from us along the muddy bottom. It’s a giant water bug! Intent on the water now, Glenn spots another and dives for it with a tiny aquatic dipnet. He comes up with a netful of mud – and the water bug!

We all work together to rinse the mud off. Kristi carefully holds the massive insect by the sides of its abdomen, avoiding the wicked sting it can deliver with its mouthparts. Another of the wetland’s voracious predators, this bug (Lethocerus americanus) doesn’t just eat other insects. Today we’ve seen several young common garter snakes (Thamnophis sirtalis) here, their yellow and red stripes contrasting vividly with their jet-black scales. Watch out, garter snakes – Glenn says that even vertebrates this large can fall prey to the giant water bug.

An extremely high-pitched song has been tugging at my ears for a while now. It’s a rapid, mechanical trill followed by a series of ticks: a katydid of some sort. And based on my observations around Helena, I suspect this is probably a cone-headed katydid (Conocephalus fasciatus), a species that seems to like wetland edges. It’s not entirely clear whether these katydids are plant-eaters or predators (reports conflict). In any case, this one is singing very close to us.

I get down on my knees, trying to track the sound. Then I spot it. The katydid is literally a foot from my ears, singing from the stem of a willow seedling. I can see its forewings quivering as it produces its shrill song. 

All the insects of the Rock Creek Confluence

Isn’t this enough insects for one little restoration area?, you might be asking. No – in fact, I’ve been leaving out a lot, trying not to make this too wordy.

But one more still deserves a mention. We notice a large, slender wasp that keeps landing on the mudflats near the giant water bug’s shallows. It’s mostly black, with crisp yellow trimlines. Its abdomen is mounted on a long, slender pedicel. It’s a predatory sphecid wasp, a mud dauber in the genus Sceliphron. Its prey: spiders. And what’s it doing here? Presumably, it’s gathering mud for another nest cell. It will fill the mud nest with spiders for its young to eat.

As adults, sometimes it’s easy to forget how amazing life is. But being out here, learning together and being in awe of the complexity around us, I remember the enthusiasm and curiosity I had as a child. As Kelly Dix remarked today, “it’s fun to be ten years old out here.” To be out with a group of passionate naturalists, celebrating the beauty of the world around us and helping with a wetland restoration project: I couldn’t imagine a better way to spend a day.

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September 7, 2022

If you’re familiar with the Carroll College campus, you’ve probably walked past it countless times. It’s a small, bushy patch of plants in front of the Corette Library, spilling exuberantly onto the sidewalk. A bunch of plants, you’re probably saying: who cares? But these plants are special. They’re from the wild, members of Montana’s native flora. And here in the heart of the city, this garden is supporting a bunch of interesting wildlife.

When you think of Montana’s wildlife, you probably think of elk, grizzly bears, bison, and sandhill cranes. And no, I’m not suggesting that you’re likely to find grizzly bears or elk stopping in front of the Corette Library. To see the wildlife in this garden, we just have to think smaller. Take bees, for instance. Among Montana’s wildlife, there are at least 399 species of bees – and that’s just bees! Besides bees, there are countless flies; colorful and harmless wasps; various spiders… To see our state’s mini wildlife, all we need is a change of perspective and a bit of patience.

So what creatures are there in this native plant garden? This article is a teaser: an introduction to the garden, a guide to some of its plants, and a few snippets about some of the creatures here. Later this winter, watch for a follow-up article where I’ll identify all of these creatures and look at what they’re actually doing here.

Planting the garden

The Carroll College native plant garden got its start in 2012. Carroll Grounds staff and many volunteers helped plant 32 species of native plants in this little patch in front of the library. It was an effort that involved the larger Helena community, too, with funding from Last Chance Audubon Society and the Kelsey Chapter of the Montana Native Plant Society.

For several years, the Carroll community continued to watch the garden, producing a report every fall on how the plants were faring. But by 2018, when I began taking classes at Carroll, it seemed that interest in the garden had waned. Unless you were one of the people involved in planting it back in 2012, it would have been easy to walk past without recognizing the garden.

The plants

But recognized or not, the plants have persisted. Ten years from its original planting, the Carroll native plant garden continues to thrive. Which plants are growing here? Let’s meet a few of the most prominent ones.

Showy milkweed (Asclepias speciosa)

Recognize showy milkweed in the garden by its lush, velvety leaves, each pair placed opposite each other on the stem. In the fall, look for the strange seed capsules, covered with warty bumps. As they dry out, they’ll release hundreds of flattened brown seeds, each attached to a white tuft of silk. The fall winds scatter the seeds to new sites. 

Showy milkweed is the plant that feeds the larvae of the well-known, rapidly-declining monarch butterfly (Danaus plexippus plexippus). This summer, I found a monarch caterpillar feeding on a showy milkweed patch in the Helena Valley. Are there any at Carroll College, as well? If you’re around next summer and you spot some, let me know!

Rubber rabbitbrush (Ericameria nauseosa)

It’s hard to miss these bushes in the fall, when their narrow gray leaves are overtopped by masses of soft yellow flowers. And today, a crowd of honeybees are busy having lunch here. They’re constantly moving from one flower to the next, burying their heads deep within the bright yellow corollas. But it’s not just honeybees – with a closer look, it’s possible to find a surprising diversity of insects on these flowers.

Blue elderberry (Sambucus cerulea)

The tallest shrub in the garden, recognize blue elderberry by its clusters of powdery, whitish-blue berries. If this bush were growing a few miles outside of town, I’d be expecting black bears or grizzly bears to come in and strip these juicy fruits. Here in the middle of Helena, watch for robins, cedar waxwings, or other fruit-eating birds to come and harvest the bounty.

Lewis’s flax (Linum lewisii)

The leaves of Lewis’s flax are delicate and easy to overlook, but the flowers are hard to miss. They’re flat, showy, five-petaled blue blooms. This is a common grassland species across Montana, and it can flower for months through the summer. The fruits look like miniature tan pumpkins. Watch for a variety of small bees on these flowers.

Canada thistle (Cirsium arvense)

Oops! This prickly plant, with its feathery pink flowers and fluffier tufts of seeds, isn’t native to Montana. And why someone decided to name it “Canada thistle,” I don’t know: it’s actually native to southeastern Europe. This plant is a “weed” that has crept into the native plant garden uninvited. But as long as it’s here, it is providing some habitat for wildlife. I spot an orange hoverfly, camouflaged to resemble a honeybee, visiting the thistle flowers.

Wood’s rose (Rosa woodsii)

Back to the plants that are “supposed” to be here. In this garden, Wood’s rose is easy to identify: just look for a rose bush with lots of red fruits and spaced-out prickles along the stems. When it’s flowering in June, Wood’s rose is a magnet for pollinators. And will any birds come to the garden this winter to eat the fruits? Let me know if you see any!

Common snowberry (Symphoricarpos albus)

Its leaves look like mouse ears and they’re arranged in pairs on the stem, just like showy milkweed. The flowers are tiny pink bells. By the winter, if they get pollinated, they’ll be replaced by globe-shaped, waxy white fruits. Watch for bumblebees and striking, spiny-haired flies visiting these flowers. In wilder parts of Montana, these bushes provide excellent cover and nesting sites for songbirds such as lazuli buntings. 

Maximilian sunflower (Helianthus maximiliani)

This plant is similar to the sunflowers that farmers grow for birdseed and Spitz snacks – but while those sunflowers must grow from seed each year, Maximilian sunflower plants are perennials that live for multiple years. The flowers are smaller, too. But just like the annual sunflowers that produce birdseed, these plants can attract quite a diversity of wildlife to the garden. Some species of bees are specialists on sunflowers. And once the flowers fade and the seeds get ripe, watch for American goldfinches coming in to feed on them. 

The wildlife

Plants, plants, plants, you may be thinking – what about the wildlife? Here’s a quick sketch. Note that this is all just from a couple of hours in the garden on one fall morning, September 7, 2022. As the weather and the plants change through the year, the wildlife you could see here is going to change, too. 

The honeybees are everywhere this morning. There are hundreds of them, hungrily visiting the rabbitbrush flowers. It’s like lunchtime at the STAC [the Carroll College dining hall, for those who may not know], honeybee-style. And the honeybees aren’t the only wildlife on the rabbitbrush today. Several bumblebees join them in the flower-feeding frenzy. (These may be Hunt’s bumblebees, Bombus huntii.) There are also a few woodland skippers (Ochlodes sylvanoides), triangular orange butterflies prone to rapid escape flights when disturbed.

A few grasshoppers are resting on the snowberry leaves and the rabbitbrush flowers, taking a break from chewing holes in plant leaves. And then – what’s that? A banded garden spider (Argiope trifasciata) has built her web in the shade of a rabbitbrush bush. And in her web, lightly mummified in silk, is a grasshopper. Chewing holes in the garden plants has its risks!

Carroll College’s tinier wildlife

Some of the other wildlife in the garden today are harder to see. But I’m looking closely – and I’ve got an insect net with me. I’ll be collecting specimens of some of these harder-to-identify creatures – and once I’ve learned more about them in the lab, I’ll be able to share their stories in depth this winter. I spot several solitary wasps on the rabbitbrush flowers. They’re black with yellow lines across the abdomen. Much smaller than yellowjackets, they’re also much less aggressive. You probably wouldn’t notice them unless you were looking.

There’s a fuzzy bee fly with dark wings on the rabbitbrush. Another has wings that are entirely clear. I spot a white-haired bee with long antennae. Another bee is small with white lines across its abdomen. A large black wasp with a narrow waist is investigating the rabbitbrush leaves, and nearby a brilliant green fly is resting. Several hoverflies that mimic honeybees are visiting the rabbitbrush and Canada thistle blooms. A tiny wasp with a long ovipositor takes off from the rabbitbrush, while a spiny black fly lands on a snowberry flower.

In roughly an hour of watching and netting, I collect 15 insect specimens. It’s a sample of just a few of the species of wildlife that this garden is supporting today. This winter, watch for more details about these particular insects.

Sed vitae

And in the meanwhile, if you ever need a break from your daily routine, consider stopping by the Carroll College native plant garden. You probably won’t see grizzly bears or bison here. But you’re very likely to see a few of Montana’s smaller wildlife – creatures that are around us all the time, but that we may not know as well as the large mammals. 

Ten years ago, Carroll College and the community came together with foresight to plant this garden. Perhaps a bit forgotten, it’s still an educational resource, a complex world in miniature, and a reservoir of biodiversity in a time when biodiversity is rapidly declining across the globe. It’s a place that we, the community, created – a place that’s full of life. Quiet and unadvertised, but in plain sight for all of us to appreciate, it’s a silent testament to the Carroll College motto: non scholae, sed vitae. And indeed, this garden in front of the Corette Library is a place that’s for life.

Further reading

Wilson, J.S. & Carril, O.M. (2016). The bees in your backyard: a guide to North America’s bees. Princeton, NJ: Princeton University Press.

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August 29, 2022

It’s a patch of pale purple among late summer’s dry crested wheatgrass (Agropyron cristatum) and the buzzing songs of the insects. A couple of checkered whites (Pontia protodice), their wings tattered, are landing to sip nectar. It’s one of our purple asters: one of those beautiful plants that, through no fault of its own, gives botanists headaches. The problem is just that there are so many types of purple asters – identifying species can be difficult.

But the checkered whites, the striking orange and black tachinid flies, and the occasional bee visiting these flowers don’t seem too concerned about the botanist’s dilemma. The crested wheatgrass that dominates this site is another of our non-native grasses that typically forms simplified, low-diversity stands. And among what seems to be a biological desert of crested wheatgrass, this aster patch is a comparative oasis of activity. 

Looking closer

To identify this aster, we’re going to have to take a closer look at it. This patch is in full bloom today, though a few of the flowerheads have already matured. Each of these mature heads is tipped with a silky tuft of hairs. The hairs will help the seeds disperse, carrying them to a new home on a breath of wind.

Like all of our asters, each daisy-like purple flowerhead is actually not just one flower, but many. In this case, there are flowers of two different types. Each purple, petal-like structure is an individual ray flower, the corolla flattened to resemble a petal but narrowing into a tube at the bottom. And within the sun-ray assembly of these flattened, lavender ray flowers are dozens of disk flowers. These don’t look at all like petals. Each disk flower is a yellow tube, surrounded by the tuft of hairs that will eventually carry the seeds on the wind. Within each tube is a yellow stigma, forked into two branches and protruding outwards. This is the structure that is ready to receive pollen as the tachinid flies and checkered whites brush past.

To identify an aster

I won’t bore you with all of the steps it takes to identify this plant. I’m using the Manual of Montana Vascular Plants, a dense and indispensable reference that contains step-by-step identification keys with almost every wild plant known from Montana. To identify purple asters, we have to pay close attention to the leaves and the flowerheads. We also have to look carefully at the involucral bracts, a series of leafy green structures that surround the flowerhead. The identification process also involves a lot of guessing and checking. Are the involucral bracts “strongly imbricate” – that is, strongly overlapping – with tips that are often purple? Or are they “somewhat imbricate” without purple tips? This helps us distinguish between asters in the genera Eurybia and Symphyotrichum.

When in doubt, identification is a process of elimination. Unsure about whether the involucral bracts are “strongly imbricate” or only “somewhat imbricate,” I start by reading about the species of Eurybia. None of them match the characteristics of the plants in front of me – so what I’m looking at isn’t a Eurybia. It must be one of our Symphyotrichum species.

Noticing the details

I continue through the ID process. Eventually, I arrive at one species that seems to match what I’m seeing: western aster (Symphyotrichum ascendens). And in the process, I’ve noticed a variety of intricate details about the plants in front of me. These details are somewhat technical, so feel free to skip over them. But I share them here to give an idea of the aster identification process:

• The involucral bracts are not glandular, nor do they curve back away from the flowerhead.
• These plants are rhizomatous, forming a loose patch connected by underground stems.
• The leaf surfaces are only sparsely hairy.
• Unlike some asters, the stem leaves do not clasp the stem with ear-like lobes.
• The basal leaves are oblanceolate and entire (without teeth on the margins).
• The hairs on the stems are not arranged in vertical lines from the leaf bases.
• The outer involucral bracts are definitely shorter than the inner bracts.
• The leaves have minute, stiff hairs along the edges.

Double-checking

Now it’s time to check my identification. Does this Symphyotrichum ascendens actually look like what I’m seeing? Is it growing in a habitat that makes sense? Western aster, Symphyotrichum ascendens, is described as a plant of mostly dry habitats like grasslands and roadsides. That corresponds with what I’m seeing here. I also take a look at Dr. Matt Lavin’s Flickr site. This is an excellent resource for information about many of our local plants, with high-quality photos and various field notes about habitat and ecology. And indeed, Dr. Lavin’s habitat notes also match with what I’m seeing. He describes western aster as a plant that’s typical of somewhat disturbed sites, such as along trails. And his photos of the plant correspond well with this patch.

The identification seems solid: this is western aster (Symphyotrichum ascendens). But the identification process has been much more than just slapping the right name on this patch of flowers. It’s been a process of getting to know them. Hopefully, from now on, I’ll be able to recognize western asters wherever I see them. I’ll be able to notice the patterns: where this aster grows on the landscape, how it changes through the seasons. 

Symphyotrichum ascendens: not just any aster

From a distance, it might be easy to overlook western aster. These plants don’t shout for our attention: they’re just a pretty patch of late-summer native flowers, blooming quietly among a desert of crested wheatgrass. But up close, this plant has a story. The complex architecture of flowers, leaves, and involucral bracts allows us to recognize this species. It’s not just some unknown kind of purple aster anymore. This is western aster, a grassland species that, based on Matt Lavin’s observations, can thrive on rather-disturbed sites. If we see a purple aster in some other habitat -high up in the mountains, or growing along the edge of a stream – it’s probably a different species, with its own story and its own habitat affinities. (For example, compare this plant to the smooth blue aster, Symphyotrichum laeve, that I looked at two weeks ago in a Missoula yard. Smooth blue aster tends to grow in somewhat moister habitats than western aster.)

Five species of insects collected from Symphyotrichum ascendens for species identification this winter.

And among the crested wheatgrass at this edge of the Helena Valley, western aster is a place of gathering. It’s an oasis of flowers that brings together bee flies, checkered whites, and spiky orange tachinid flies. Today I’ve collected a few of these insects, so this winter I’ll be able to learn more about their stories, too. What are the lives of these diverse insects that have come together here, to feed on western aster nectar and to brush pollen onto the yellow stigmas? 

Recognizing the patterns

Western aster and its insect visitors: it’s another handful of the late-summer stories of this landscape. And as we start to recognize this plant, to become familiar with the insects that visit it, we have another point of connection with the landscape around us. 

So next time you’re out for a walk, keep an eye open for a patch of western aster, blooming among the grasses along the trail. If you want to be sure, grab a magnifying lens and a copy of the Manual of Montana Vascular Plants and give the identification process a try. And let me know which insects you’re seeing on these flowers!

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August 18, 2022

Sometimes, a day in the field doesn’t go as planned. I had started out this morning thinking that it would be a pollinator identification day. The setting: Carol “Kate” Wilburn’s urban Missoula yard. Since 2019, Kate has been converting her lawn into a garden packed with fruit trees and wildflowers. There are apples, currants, peaches, and apricots growing with dozens of species of native plants. She wants to have a yard where she can grow food, create wildlife habitat, and hold educational programs. Today, I wanted to take a look at the wildlife habitat. In a cityscape dominated by asphalt and houses, what creatures show up when we plant native plants?

In spite of the summer’s heat, Kate’s yard has been a profusion of flowers this year. At this season, there are five plants in particular that stand out: purple coneflower (Echinacea purpurea), smooth blue aster (Symphyotrichum laeve), Rocky Mountain beeplant (Cleome serrulata), Missouri goldenrod (Solidago missouriensis), and Maximilian sunflower (Helianthus maximiliani). When I arrived here and saw this palette of pink, purple, and yellow, several questions came to mind. How much diversity could we find here? What patterns would we see?

Kate is not just an avid gardener, but also my mom. We’ve been talking for months about doing a blog post on the insects in her yard. It seemed like a great opportunity to combine a visit with a check-up on her garden. Were the native plants really providing habitat for lots of insects here, as we hoped?

The best-laid plans

The plan for this field day was simple. We would spend time focusing on each of these five plants, observing patterns of insect activity. We would also catch some of the representative flower visitors, sneaking up on them and popping them quickly into plastic vials. Just like I did with bumblebees last month, we would put the vials on ice in a cooler to let the insects chill. Then we would take photos of the chilled insects, identify them, and let them fly off.

The day was already hot when we started, with the sun near its zenith and the temperature climbing rapidly toward the 90s. We began with the purple coneflower. The insect-catching went well. Within 15 or 20 minutes, we had an assortment of bumblebees and orange skippers in plastic vials.

It was at the “identify them” stage that the plan started to go awry. Whether it’s a fluke of nature or some malicious taxonomic conspiracy, it seems that for every common species of skipper butterfly (family Hesperiidae), there is at least one other that looks nearly identical. We spent most of an hour cross-checking two different field guides, maneuvering recalcitrant skippers in a butterfly viewing cage, and debating. Eventually, we decided that the butterflies we were seeing were all a common, remarkably variable species, the woodland skipper (Ochlodes sylvanoides).

Bees and their identification

Then it was on to the bumblebees – and they weren’t much better. The identification keys I have require females, but most of these bumblebees were males. We tentatively identified them as Hunt’s bumblebees (Bombus huntii), but we couldn’t be sure.

We finally came upon a female bumblebee, her abdomen mostly black with a yellow band at the base. This one would be straightforward, I thought! The cheek length of a bumblebee is both one of the most important characters for identification, and also one of the most difficult to discern. Quite sure that I was seeing a cheek that was as long as wide, I reached a dead end in the key. Perhaps it was slightly shorter than wide? Or slightly longer than wide? She was already warming up and beginning to wiggle. I took various photos and let her fly off, hoping that in the future I might learn to identify her.

Then it came time to look at an even-smaller bee, her hind legs coated in pollen. I flipped to the right page in my identification guide and took her off of the ice. Almost immediately, she began to twitch and wake up. I only had time to get a few photos and admire her briefly before she flew off. I looked back at the key, feeling defeated. Did she have just one subantennal suture or two? Was her tongue long or short? Forget it! Maybe this is why bee biologists usually work with specimens, I thought.

Too much

I needed to adjust my expectations. Clearly, identifying all of these insects in the field was way more than we could reasonably achieve today. So instead, we did something that anyone can do in their yard. We watched flowers, took photos, and tried to distinguish different “species” in the field by shape, size, and appearance.

And although we ended the day with many questions still unanswered, what we saw was compelling. In Kate’s urban yard, each of these five plants is supporting a variety of insects. Each plant is unique, with its own community of pollinators. So come along with us on this journey: five plants, one afternoon, and a surprising diversity of insects in one small city yard.

Purple coneflower (Echinacea purpurea)

The purple coneflower is a crowd of pastel, magenta-and-orange flowerheads rising above roughly textured leaves. This species is one of those wildflowers that wouldn’t be here without some human help. Although its cousin, narrow-leaved coneflower (Echinacea angustifolia) is a Great Plains species whose range extends into eastern Montana, purple coneflower is a plant of eastern North America’s wet prairies and meadows.

Of the five plants we’re looking at today, this is the only one that isn’t actually native to Montana. In general, native plants are especially important for our local insects: the plants and the insects have been evolving together for millennia. Nevertheless, the purple coneflower is busy with bumblebees and orange skippers today. We also spot a few tiny bees that invariably seem to escape when we try to slip up on them with a vial.

Most of the bumblebees are those males with orange-banded abdomens that we tentatively identify as Hunt’s bumblebees (Bombus huntii). We also catch a female who remains a mystery, her abdomen boldly clothed in yellow and black.

Along with the bumblebees, an assortment of woodland skippers (Ochlodes sylvanoides) are nectaring here. This is a very common late-summer butterfly across much of the west. An adaptable habitat generalist, its larvae can develop on various native and introduced grasses. The adults visit a range of flowers.

A few more bees

In about 15 minutes of observation, we spot just a single honeybee (Apis mellifera) here. So honeybees are visiting the coneflower, but not very commonly.

We also manage to catch two small bees. The first is smaller than a raisin, her hind legs dusted with deep yellow pollen. Each segment of her abdomen is tipped with bands of fine white hairs.

The other bee is larger, also with a banded abdomen. Its eye is pale green and the tip of its abdomen bears a prominent, spiny structure.

Except for the small, white-banded bee, none of these visitors seem to be carrying pollen. Are they only collecting nectar from the coneflower?

Smooth blue aster (Symphyotrichum laeve)

The asters are busy clumps of pale lavender blooms, appearing feathery from a distance. The flowers are loaded with more nectaring woodland skippers, their tongues unfurled. The other common insects here seem to be a variety of medium and small bees. The most common are approximately raisin-sized. Like the smaller bee we found on the coneflower, they have white bands of hair across the abdomen. These bees are clearly females, collecting pollen on their legs. They make a barely audible hum as they buzz busily from flower to flower.

We spot another species that looks similar but is clearly smaller. From time to time, we also see a few bees with remarkably long antennae here.  

The asters are very active with all of these takeoffs and landings. Just on these two plants that we’re watching, we’re seeing probably a dozen skippers. At any instant, there are close to forty bees on them.

Unlike honeybees and bumblebees, these are very likely solitary species, each female provisioning her own nest with pollen and nectar to feed her young. Honeybees get lots of press, but the diversity of solitary bees is incredible. Many of them are raisin-sized or smaller, like those we’re seeing here. Lots of them nest in the ground; others nest in hollow plant stems. And the fact that they’re here, in urban Missoula, tells us that these species are finding what they need to survive. I wonder how far they’ve flown to find these flowers.

Seeing the diversity

We keep spotting additional species. There’s a little bee – or is it a wasp? – with a grayish abdomen, yellowish legs, and some yellow markings on the face. 

Another bee looks like the green-eyed spiny one from the coneflower. We can’t know for sure without collecting both, but it seems likely that they’re the same species.

Nectaring alongside all of the woodland skippers, I notice a different butterfly. It’s similar to them in size and shape, but has much crisper white markings on the orange-green hindwing. I catch it for a closer look. After much study and debate, we decide that it’s probably a common branded skipper (Hesperia comma). Or could it be a western branded skipper (Hesperia colorado)? In either case, it’s another widespread member of our late-summer butterfly fauna. The caterpillars feed on grass, and the adults find nectar on a variety of flowers. 

Rocky Mountain beeplant (Cleome serrulata)

The beeplants have already been blooming for weeks, but there’s no end in sight. The pale purple flowers, with their long, protruding stamens, surround tight clusters of darker, unopened buds. These plants are annuals, growing from seed each year. Nevertheless, they’ve thrived for several years now in Kate’s yard, reseeding happily. Some of this year’s plants are as tall as I am.

These flowers are by far the most popular today with the honeybees (Apis mellifera). But this afternoon, we’re not seeing very many other insects visiting them. Compared to the smooth blue aster, the activity level here is basically nothing. We spot a single woodland skipper. There’s the occasional medium or small bee that flies off before we can get a good look. I also notice several shiny ants crawling around on the stems and unopened flower buds. What are they doing? They don’t seem to be visiting the open flowers.

Watching the bees

As always, observing insects in the field is humbling. There’s so much more out here than what we can photograph or catch. A bumblebee moves briefly from flower to flower. Its abdomen is mostly yellowish, and I suspect it may be a white-shouldered bumblebee (Bombus appositus). I decide to try for photos instead of catching it in a vial. It bounces from flower to flower and I follow it with my camera, just a little bit too far behind. Then it flies off, and I have neither the bee nor its photo.

I watch the honeybees here more closely. Their pollen baskets are empty, and they seem to be poking their heads deep inside the flowers instead of paying attention to the widely spreading stamens. They aren’t bothering with pollen; presumably they’re collecting nectar here.

A black and white wasp is flying from cluster to cluster. But like the ants, it’s paying attention to the flower buds rather than the flowers themselves. It’s another mystery that we won’t unravel today.

Missouri goldenrod (Solidago missouriensis)

The goldenrods are sprawling, enthusiastic fountains of yellow covered in the activity of various small insects. Many of the plants are knee-high, evidently appreciating the water here. In their usual, sun-baked grassland habitats, Missouri goldenrod stays much shorter.

Wasps are common here this afternoon. I catch a prominently striped, yellow and black species: probably a predatory wasp in the family Crabronidae. If I’m right about the family, these are wasps that specialize in hunting various other insects. Some hunt beetles, some hunt caterpillars, and some even hunt other wasps and bees. They carry their prey to their nests, providing food for the larvae. The adults, on the other hand, feed mostly on flower nectar.  

Another wasp is a little bit larger and blacker. A broad, prominent yellow band crosses the abdomen, which comes to a distinct point. These wasps are more skittish than the bees, and it’s difficult to catch them.

We see the occasional, medium-sized pollen-collecting bee here, resembling those we found on the smooth blue aster. There are also several well-camouflaged, speckled tan bugs visiting these flowers.

Maximilian sunflower (Helianthus maximiliani)

Almost as tall as the beeplants, these perennial sunflowers form vigorous, upright patches with bright yellow flowerheads and sandpapery green leaves. The sunflowers in this yard are a bit of a botanical mystery. They were sold as Maximilian sunflower, and seem to have some characteristics of that species, a native of eastern Montana. But while Maximilian sunflower leaves are usually folded in half along their midvein, like small green canoes, these leaves are more relaxed. This makes them look more like Nuttall’s sunflower (Helianthus nuttallii), a common species in our intermountain part of the state. In either case, these are striking plants. And the bees seem to be loving them.

We catch a medium, hairy gray individual with sky-blue eyes. Another one, densely covered in white, has hairy scoops on its forelegs.

There are several tiny bees with blunt abdomens. A couple more woodland skippers and what appears to be another Hunt’s bumblebee are visiting these yellow blooms.

One bee has extremely long antennae, green eyes, and a stiff covering of hairs. Another is small and narrowly cylindrical, with yellow markings on the legs.

Bees and beetles

A few of these bees – like the one with the long antennae – seem similar to species we saw earlier on the smooth blue aster. But many of these bees are new to us today. As with the other five plants, the insect community on the sunflowers is largely unique.

Kate spots a solitary beetle, medium-sized and brassy-haired, on the sunflower blooms. This is a blister beetle (family Meloidae), probably Epicauta ferruginea or one of its close relatives. The adults feed on the foliage and flowers of sunflowers and related plants – but the larvae are specialized predators in the soil, hunting down grasshopper egg pods and feeding on the eggs. Grasshoppers are rare in the middle of the city, so this blister beetle is a special find.

Catching glimpses

One urban Missoula yard, surrounded by asphalt and lawns. Four species of native plants, and one immigrant from the tallgrass prairie. What we’ve seen today is just a glimpse of this community, but it’s a tantalizing one. Each of these flowers is different – not just to our eyes, but to the insects’ eyes, too. Each patch holds its own stories of the pollinators it supports. For the purple coneflower, it’s the stories of nectaring bumblebees and woodland skippers. The smooth blue aster supports more skippers and a variety of pollen-collecting bees. The Rocky Mountain beeplant is feeding honeybees, ants, and a smattering of less-common visitors. For predatory wasps, the Missouri goldenrod is proving important today. And the Maximilian sunflower is harboring yet other species of bees.

There’s so much more we could ask here. Which bee and wasp species have we seen today? What are their life histories? Are they floral generalists or specialists? Twig nesters or ground nesters? But to answer those questions would take a much more intensive project, or someone much more skilled with bee identification than I am.

The bees and their flowers

We can’t answer those questions today. But anyone can go out in their yard and do this. Anyone can glimpse the sorts of general patterns that we’ve seen. In Kate’s yard, it seems, each of these flowers is adding something unique to the pollinator habitat that’s present. And they aren’t growing in isolation: there are also fruit trees, vegetables, and dozens of other native plants here. Some bloom earlier, some later.

The plants in this yard have only been here for two to three years now. But already, by spending part of a single day looking at five flowering plants, we’ve tallied 21 species of insects on these blooms.

It would take more sleuthing to learn the full stories of the insects we’ve seen today. But anyone can plant native flowers in their yard. Anyone can go outside, sit next to a patch of blooms, and spend a few minutes getting acquainted with the insects they’re attracting to our yards.

And if you’re looking for a few more beautiful, hardy native plants to boost pollinator diversity in your yard, here are some ideas.

Further reading

Glassberg, J. (2001). Butterflies through binoculars: the west. Oxford, UK: Oxford University Press.

Montana State University. (n.d.) Bumble bees of Montana. Retrieved from http://mtent.org/projects/Bumble_Bees/key_female.html

Pyle, R.M. (2002). The butterflies of Cascadia. Seattle, WA: Seattle Audubon Society.

Wilson, J.S. & Carril, O.M. (2016). The bees in your backyard. Princeton, NJ: Princeton University Press.

The post Five late-summer wildflowers and the complex world of their bees appeared first on Wild With Nature.

July 31, 2022

I’m standing along Helena, Montana’s Centennial Trail on this hot summer evening, contemplating a mystery. The mystery is a plant: Mentzelia decapetala, ten-petal blazingstar. Tightly closed, luminous white flowers rise above the toothy, sandpaper-textured leaves. Mentzelia plants, with their massive blooms and unique foliage, would be striking in any garden. But here they seem to be thriving without anyone’s care, a group of native plants in the middle of the city, growing along an abandoned railroad track. Like bold, living sculptures, they pose questions without offering obvious answers. I can’t help but wonder: what lies beneath their showy appearance? What’s the story of these plants’ lives?

When I do a quick Google Scholar search, I’m surprised to find that very little has been written about the ecology of Mentzelia decapetala. These plants are truly a mystery: I can think of so many questions. The leaves are so rough that they stick to my fingers and pant legs. Why such sticky foliage? The flowers are massive and showy, but right now they’re tightly closed. When do they open? Which insects pollinate them? Around Helena, these plants are closely associated with barren habitats: rockslides, sparsely vegetated slopes, abandoned railroad tracks. It seems incredible that they even survive – let alone thrive – in such harsh places.

Before I make any more field observations, I decide to do a more thorough search of the literature. And here and there, mostly in articles about related Mentzelia species, I find some tantalizing hints. These bits and pieces all seem to be pointing to what I had originally suspected: the story of this plant is a remarkable one. 

Mentzelia pumila, the death trap plant

Through my reading I learn that a close cousin, Mentzelia pumila, is also covered with clinging hairs. If we zoom in with a microscope, we can see that these hairs form a thorny forest of hooks and barbs, lying in wait to snag passing insects. It’s a death trap where these insects perish slowly, their wings or legs caught on tenacious hooks. According to scientists Thomas Eisner, Maria Eisner, and E. Richard Hoebeke, during their study the Mentzelia pumila plants “seemed invariably to have numbers of dead insects stuck to them.” It appears that these miniature, deadly forests of hairs can catch almost any type of insect that visits this plant. They did find one exception, though: the aphid Macrosiphum mentzeliae picks its way slowly through the hairs, avoiding the deadly barbs. Hidden among a dangerous, microscopic forest, this aphid manages to make a living feeding on Mentzelia pumila.

Why is Mentzelia pumila covered in these gnarly traps? It seems to be a defense against herbivores. But in their article, Eisner, Eisner, and Hoebeke suggest that this plant might also be passively hunting insects, benefiting from the additional nitrogen that their corpses might contribute to the soil nearby.

Fly killers, bee lovers

Could the clinging hairs of Mentzelia decapetala act similarly? Eventually, I unearth a hint that they may. It’s a brief mention in an 1879 journal, hiding under the antiquated name of Mentzelia ornata. (This name was historically used for M. decapetala.) Watching this American plant in a French garden, where it had been planted, an observer found flies visiting the foliage, apparently attracted to a fluid secreted by soft, glandular hairs among the stiff barbs. The flies would frequently find themselves caught by the barbs. They would either die there, trapped, or pull their heads off in their frantic efforts to escape. Flies, don’t land here! This plant is a death trap!

I also find an article about another related species, Mentzelia nuda. This one discusses pollination and suggests that, unlike the leaves, Mentzelia flowers can have a more positive relationship with insects. This study documents a variety of bees and several small flies visiting Mentzelia nuda blooms. Among these bees are two Mentzelia specialists, Perdita wootonae and Andrena mentzeliae. There are also various generalist bees, including the golden northern bumblebee (Bombus fervidus). Mentzelia nuda flowers produce nectar deep inside, among the dense stamens. And in this species, nectar production actually lasts for about 10 days after the petals fall, attracting ants to the developing fruits. The ants seem to defend the seeds against the beetles and moths that attack them, increasing seed production.

More from the literature: from flowering to dispersal

Mentzelia nuda flowers open in the late afternoon and close near sunset. Not so for our Mentzelia decapetala, according to the only study I can find that discusses pollination in this species. This study, from Nebraska, tells of flowers that open about an hour before sunset and close again near midnight.

In the Nebraska observations, honeybees and sphinx moths were the most common insects that visited Mentzelia decapetala flowers. The researchers also found bumblebees, grasshoppers, and a few other moths on the flowers.

This patchwork of information gives us a tantalizing sketch about the life of Mentzelia decapetala. It’s a plant of contradictions, finding a way to make a living in barren, dry habitats. A flower of the dusk and the night, it feeds bees and sphinx moths. The leaves, on the other hand, are a miniature forest of wicked, barbed spines: a graveyard for unwary insects. Another paper reports that the seeds are winged, scattered to new homes by the wind.

It’s a fascinating sketch of a plant, but it’s far from complete. And is this sketch even accurate for our local Mentzelia decapetala patches around Helena? It’s time to head out into the field and find out.

Into the field: afternoon at Devil’s Elbow

August 2, 2022

It’s a hot, windy mid-afternoon. I’m standing on a steep, shaley, southeast-facing slope near Devil’s Elbow Campground, baking in the summer heat. There are hundreds of Mentzelia decapetala plants here, growing up out of the hot shale. All of the flowers are tightly closed right now. So far, this matches with the Nebraska study: this plant definitely isn’t an afternoon bloomer.

I start searching the foliage, looking for insects. Will I find any of them trapped here, like the large numbers that have been found on Mentzelia pumila? At first glance, I’m not finding trapped insects. Instead, I find spots of a dark, viscous, sticky substance on the leaves. It looks like molasses. I taste a little bit. Surprisingly, it’s slightly sweet like molasses, too, though there’s a bitter aftertaste.

I’m amazed to find a Mentzelia plant that’s been browsed, the tips of its stems bitten off. This is a total surprise – what would eat these hairy, sandpapery plants? Could it be deer? As a gardener, I know that deer have an incredible ability to eat seemingly unpalatable vegetation. But I can’t imagine that even a deer would enjoy such an unpleasant-textured plant.

I find a stem with marks of an injury, and there’s this same blackish liquid congealed near the wound. This seems to confirm what I’ve already been starting to suspect: this black substance is Mentzelia sap.

Not far away, I find a few more stems that have been bitten off near their tops. Surprisingly, though, even though I’ve checked about a dozen plants, what I’m still not finding is any sign of trapped insects. I haven’t yet seen a single invertebrate stuck among the hairs, unlike what the literature records for this plant’s close relative, Mentzelia pumila.

Deadly hairs

And then, as soon as I think that, I find my first insect victim. It’s a tiny fly, about 2 millimeters long, black with red eyes. It’s slightly shriveled and very dead. Its legs are stuck among the forest of hairs, on a bract below a flower bud.

Now my search for tiny creatures becomes more productive. A medium-sized spider skitters from among the flower buds, untrapped and very much alive. Clearly some invertebrates are able to get around in spite of the hairs. And at least on this species of Mentzelia, it’s not just aphids.

Next I spot a small, soft-bodied fly. This one is another casualty, stuck to a drop of sap below a flower.

Unfazed weevils and a struggling moth

Now I notice a small, blackish weevil. Like the spider, it’s not trapped at all, crawling nimbly along the stems and across the flower buds. In my literature search, I found an article by Kathleen Keeler reporting the weevil Orthoris crotchi as a seed predator on Mentzelia nuda. Perhaps the weevil I’m seeing is Orthoris crotchi or something similar: a seed predator on Mentzelia decapetala.

As I part the leaves to check for insects, they catch on my fingers. It’s an interesting sensation for me, though clearly a deadly one for some insects. Others navigate the hairy forest unimpeded. I spot a second weevil on a flower bud, crawling quickly across.

Next I find a narrow-winged moth, perching on another flower bud. It’s still alive, but it struggles as I get photos: a leg is stuck among the barbed hairs. Why is it that the Mentzelia foliage is a death trap for some creatures and not for others?

I walk past several more plants whose tops have been browsed. I wonder if a mule deer in the neighborhood has a stomachache right now.

More creatures among the foliage

I keep checking more Mentzelia plants, especially focusing on the clusters of flowers and buds where I seem to be finding the most invertebrates. But the search has slowed down again. I’ve found a few more weevils, none of them stuck. Insect prey trapped here at this season seems sparse.

I spot a tiny spider, gray with black speckles on its abdomen, hiding among the flowers. It jumps onto my finger and then I release it back where I found it.

It’s still early in the bloom period here. Many plants only have green flower buds. Various others are within their flowering window, the bulky white petals wrapped tightly together in the afternoon heat. Only a few plants have immature fruits yet, their white petals fallen to the ground and the green capsules swelling with seeds.

Attracting ants?

I check the tops of these few developing fruit capsules. If this was Mentzelia nuda, I would expect (based on the literature) to find the tops of these fruits still producing nectar, attracting ants to protect them. The literature told me nothing about whether Mentzelia decapetala might attract ants in the same way, so it’s up to me to check.

So far, it seems that the answer is no. I’m not seeing any ants visiting these fruits, and the tops of the capsules appear dry rather than sticky. Unless I’m missing something, it seems that Mentzelia decapetala stops producing nectar when it stops flowering.

On the hairy margin of a developing Mentzelia fruit, I spot another medium-sized black fly. It’s upside down, shriveled, and dead. So far, flies seem to be the primary victims of this plant’s clinging hairs.

Then I spot another trapped moth, this one tan with black speckles, its wingspan as wide as my thumb. It’s stuck to the flower bracts. 

The sun will shine on this slope for hours longer today, but already the shale is blistering hot. It almost burns my bare leg as I kneel on it. 

Lessons in the heat of the day

I haven’t found a single open flower here this afternoon. The smooth, waxy white petals are clenched tightly, just like researchers reported in Nebraska.

This Mentzelia population is a mix of sizes and shapes. There are the tall, branching plants I’ve been checking for insects. Between them, low to the ground, there are smaller plants. So far, these ones are just rosettes of deeply toothed leaves. And scattered among these two forms, there are also the dead, bleached skeletons of plants from previous years.

This mixture of rosettes, flowering plants, and dead skeletons says “biennial” to me. And indeed, the Manual of Montana Vascular Plants reports this life cycle for our populations of Mentzelia decapetala. Biennial plants typically live for two years. In the first year, they start out as a low cluster of leaves. In the second year, they grow taller and flower – and then they die. But they live on through their seeds, which give rise to the next cohort of young plants.

It’s sweltering out here, and I’m ready for a break. But before I go, I find another flower with a small, midge-like fly trapped on it. I collect this one and bring it back so that I can take a closer look in the lab.

What have we learned out here? It seems that, at least at this season, trapped insects aren’t very common on these plants. Would this picture change later in the year? Or is Mentzelia decapetala just less of a fly-catcher than Mentzelia pumila? It’s impossible to tell without watching these plants over a longer time. But it’s clear that these hairs are an effective trap for some insects – especially soft-bodied moths and flies. 

From dawn to dusk: Mentzelia along the tracks

August 3, 2022

It’s almost an hour before sunrise, and I’m back among the Mentzelia decapetala plants along the Centennial Trail. At this hour, the flowers are all tightly closed. They glow softly in the blue-white glare of the streetlights.

Closed flowers in the afternoon, closed flowers before dawn. It matches with the Nebraska observations, the only published information I found on the flowering of Mentzelia decapetala. So far, it seems that Helena’s Mentzelia behave like Nebraska’s Mentzelia, opening shortly before sunset and closing sometime during the night.

Hairs under the microscope

Later in the day, I stop at Carroll College. I want to use a high-powered dissecting microscope to take a closer look at the Mentzelia leaf and flower that I collected the day before. Under the microscope, I can see that the plant’s protective hairs have tiny barbs along their entire length. The hairs seem to be longest and most prominent on the bracts that surround the flowers. This is also the region of the plant where I’ve found the most trapped moths and flies so far. Are the hairs a system of protection for the flowers, in particular? Each hair looks like a miniature, extremely narrow-crowned fir tree – or perhaps a weapon from a nightmare. As we’ve seen, for certain flies and moths, perhaps “nightmare weapon” is indeed the best description.

Strangely enough, the small fly that was trapped here yesterday has disappeared! Only a few leg fragments remain to tell me that I didn’t imagine the whole thing. Where has it gone? Frankly, I have no idea. My best guess is that another invertebrate – perhaps a spider – had been spending the day inside the Mentzelia flower. Stored in a plastic vial overnight, I imagine that this hypothetical predator emerged from the flower and ate the trapped fly.

Mentzelia in the evening

It’s 8:00 pm when I return to the Mentzelia patch along the Centennial Trail. The sun is sinking, but the evening is still hot: it’s 90°F right now, and the heat is made just slightly more bearable by a gentle westerly breeze. The Mentzelia flowers are beginning to open: striking, starlike white arrays with bouquets of glowing yellow stamens inside. I sniff one of them. It does have a fragrance, but the smell is delicate, just a little whiff of perfume.

Already, I’m noticing bees on these flowers. But unlike the Nebraska Mentzelia decapetala, which honeybees visited in the evening, the common visitors to Helena’s Mentzelia patch are all bumblebees.

A plethora of bumblebees

I’m carrying my insect net tonight. In short succession, I catch three bumblebees as they go from bloom to bloom. They seem to be focusing their efforts near the tips of the stamens, clambering about on them and apparently collecting pollen. 

I walk over to another large, bushy plant, growing right along the abandoned railroad spur line. This one is barely open yet, just the first few flowers beginning to unfurl. Here I spot another bumblebee. She hovers briefly near the closed flowers, just long enough to decide they aren’t worth bothering with right now, and then lands among the stamen bouquet of a barely-open bloom. 

I didn’t expect that I would be doing a repeat of last week’s bumblebee observations tonight! But I did bring a cooler of ice with me, so once again I’m netting every bee I can catch and cooling them down to identify them. 

Another bumblebee arrives at this Mentzelia plant and I net her as well. So far, every single bee I’ve seen tonight has a bold orange band across her abdomen. I’ll need to take a closer look and double-check, but it seems that these are all Hunt’s bumblebees (Bombus huntii) – the least picky flower visitors of the seven bumblebee species we found near Helena last week.

Life and death in the Mentzelia patch

It’s 8:20 now. I continue moving from plant to plant. Most of the flowers are still closed. And of the blooms that have opened, most have still only unfolded halfway. They’re white cups right now, not the white platters they’ll soon become. 

But they’re open enough for the bumblebees. I’ve caught seven individuals now, all with rusty-banded abdomens. And so far, bumblebees are the only flower visitors I’ve seen. I’ve noticed a few small, blackish weevils crawling on the outer surfaces of the flower buds – presumably the same weevil species I found during yesterday’s midafternoon visit to Devil’s Elbow. Now I spot a pair of these weevils mating on a Mentzelia leaf. Just like yesterday, they seem completely unfazed by the barbed hairs that cover the leaves.

Tonight I’m mostly focused on flower visitors, though I’m also trying to notice any insects trapped on the foliage. I’m not seeing many dead bugs: like the pattern I noticed at Devil’s Elbow, the trapped creatures seem few and far between. Nevertheless, I do notice a bee fly (family Bombyliidae) stuck to a flower bud, its wings extremely frayed. It’s been dead here for a while. 

It’s interesting to reflect on the dual nature of this plant. Its leaves can be deadly – but the weevils and the spiders seem to navigate them without trouble. Its flowers, on the other hand, seem relatively safe. I haven’t found a single trapped bumblebee anywhere. Unlike showy milkweed, whose flowers sometimes trap and kill honeybees, Mentzelia flowers seem to be trap-free for pollinators.

Approaching sunset

Like the plants at Devil’s Elbow, the Mentzelia here have just a few fruiting capsules developing so far. And again, the disks on top of these capsules are dry, without any sign that nectar is still available after the flowers have withered. There are no ants on these fruits – although I do notice a reddish ant trying to crawl into a tightly closed flower. The pattern I saw at Devil’s Elbow is getting reinforced: unlike Mentzelia nuda, it seems that Mentzelia decapetala does not attract ants to protect its maturing seeds.

It’s 8:30 now. The wind has died down and the sun is just a finger’s width above the western mountains. The evening light is becoming a rich golden. I walk over to a patch of plants on a rubble slope near the old railroad tracks. Here, the flowers are mostly open now. The bumblebees are staying very active. There are at least three just in this patch, each one diligently rummaging among the deep yellow anthers.

Bumblebee ID

Now I return to my cooler and check on the bumblebees. Am I right that they’re all Hunt’s bumblebees, or is there a surprise here? The bees I caught earliest are mostly chilled now, just twitching slightly. I run through the identification process with them. They all have moderately long cheeks, yellow hairs on the face, and bold yellow stripes across the thorax. I’ve done my due diligence now – and as I had suspected, these are Hunt’s bumblebees (Bombus huntii).

They all look similar, so I run through the identification process quickly, even managing to confirm the identity of those that have not yet cooled off fully. They’re all females, and all Hunt’s bumblebees. Most of them have very full pollen baskets, heaped high with a tawny yellow mixture of nectar and pollen. Now that I’ve confirmed their identities, I can let them all go. Freed from their vials, they shiver to raise their body temperature. Then one by one, they fly off into the fading light.

Hoverflies at sunset

Now it’s 8:40. The sun has just set behind the mountains. The Mentzelia flowers are fully open now. I notice a small hoverfly (family Syrphidae) perching on a Mentzelia stamen. It flies off as I approach. Several Hunt’s bumblebees are still active, their gentle buzzing barely audible against the background noise of traffic from Benton Avenue nearby.

I spot a larger hoverfly, also visiting the tip of a Mentzelia stamen. His abdomen is black with narrow, curved white markings. Like most hoverflies, this one is wary. He levitates above the flower before I can get a photo of him. He hovers a few feet away, controlling his position as carefully as a helicopter. I inch my insect net into position and swipe. I’m expecting he’ll dart away, evading the net – but surprisingly, I manage to catch him. I suspect he’s a white-bowed smoothwing (Scaeva affinis), a relatively large and distinctive hoverfly I’ve observed before around Helena. (And later, with a closer look, I’m able to confirm that I’m correct.) I only see this single individual, but it’s still a record of another species that is showing an interest in Mentzelia flowers. The white-bowed smoothwing is known to visit a variety of flowers; the larvae hunt aphids.

Mentzelia moths?

As the twilight fades, I’m starting to think about moths. So far, the Nebraska observations of Mentzelia decapetala seem to be a fairly good match for the patterns I’m seeing. There, the common flower visitors on these evening flowers were honeybees and sphinx moths. Here I’ve found Hunt’s bumblebees instead – a native species that, like honeybees, visits a wide range of flowers. Will I find sphinx moths, too?

By now, nearly all of the Mentzelia flowers have opened. I’m kneeling along the abandoned rail line, at the edge of an extensive patch of these white starbursts. Three Hunt’s bumblebees are still going from flower to flower here. It’s quite a way to spend an evening. I’m watching a Helena summer spectacle: one whose beauty I couldn’t really imagine until this week. Mentzelia decapetala pollination at sunset: it’s a striking contrast. I’m kneeling in a wasteland, a few feet from a car seat that someone has discarded, yet I’m in the midst of this patch of smooth white petals, exuberant yellow stamens, and sandpaper green leaves growing where no one cares about it. Still no moths, though.

Will any show up? I really have no idea. I alternate between kneeling at the edge of the patch and pacing among the plants. I’ll give the moths a bit more time.

By 9:10, the last of the bumblebees have finished their foraging for the evening. The blazingstar patch stands quiet, the luminous yellow and white flowers catching the fading light like beacons. Their scent seems stronger now, though it’s still just a delicate perfume.

I’m still waiting and wondering. Is this all for the night? Or is it just the beginning of the show?

White lines in the twilight

It’s 9:20 when I spot my first sphinx moth. It’s massive, larger than a hummingbird, far bigger than I had imagined. Its abdomen is as thick as my index finger, spotted with white. Its wings flash white and rosy as it moves soundlessly from flower to flower. I edge closer and sweep my net. Incredibly, I manage to catch it. The moth flutters in the net bag and I start walking towards my car to retrieve a butterfly observation cage. As I walk, I spot a second sphinx moth, similarly patterned, silently probing the glowing white flowers.

Watching the moth flutter in the butterfly cage I’ve retrieved, I immediately realize that its massive size isn’t the only striking thing about it. Its forewings are intricately patterned. There’s a broad, tan stripe running through the middle, intersected by narrower white veins. Occasionally I can catch a glimpse of the incredible, salmon-colored hind wing. It’s a white-lined sphinx (Hyles lineata). Looking it up, I read that the larvae of this widespread moth can feed on a variety of plants, including willowherb (Epilobium) and evening-primrose (Oenothera). And although it’s a common species, this is the first time I’ve seen one around Helena. No wonder. The adults are mostly active at twilight and after dark – times when I haven’t been out searching for them.

White flowers in the night

It’s 9:40 now. The last hint of the sun is a peachy glow to the northwest. I can see a number of tiny micro moths flying around the Mentzelia, but I can’t tell if they’re actually visiting the flowers. Another white-lined sphinx is flying around, quietly dipping its proboscis into the showy white blooms. In spite of its bulky body, it’s a fast, agile flier.

I’ve forgotten to bring a headlamp with me tonight. The flowers are still glowing, though, illuminated by the floodlights from the Batch athletic fields in the distance. But without a headlamp to help me, it’s getting difficult to see what’s visiting the flowers now. Are there other insects flitting from bloom to bloom in the night? Perhaps other moths, or nocturnal bees? It’s a question that will have to wait for another time.

But just as I turn to go, I spot another moth alighting among the stamens of a Mentzelia flower. This one is medium-sized: still substantial but maybe a quarter of the size of the white-lined sphinx. Before I can catch it for a closer look, it flutters off into the night.

There’s something I find captivating about this plant. For some insects, it’s a prickly killer, trapping small flies and moths with its miniature barbs. For others, like the weevils, it seems to be a home. And on these warm summer nights, it’s a spectacle that few people get to see: showy white flowers that open near sunset, attracting orange bumblebees and enormous sphinx moths. Among the discarded trash along this abandoned rail line, it’s nice to know that this kind of magic still exists.

Further reading

Brown, D.K. & Kaul, R.B. (1981). Floral structure and mechanism in Loasaceae. American Journal of Botany 68(3):361-372. Retrieved from http://www.jstor.com/stable/2442772

Eisner, T., Eisner, M., & Hoebeke, E.R. (1998). When defense backfires: detrimental effect of a plant’s protective trichomes on an insect beneficial to the plant. Proceedings of the National Academy of Sciences 95(8):4410-4414. Retrieved from https://www.pnas.org/doi/abs/10.1073/pnas.95.8.4410

Gray, A. (1879). The beheading of flies by Mentzelia ornata. Botanical Gazette 4(10):213-214. Retrieved from https://www.journals.uchicago.edu/doi/pdf/10.1086/325279

Keeler, K.H. (1981). Function of Mentzelia nuda (Loasaceae) postfloral nectaries in seed defense. American Journal of Botany 68(2):295-299. Retrieved from https://www.jstor.org/stable/2442861

Keeler, K.H. (1987). Survivorship and fecundity of the polycarpic perennial Mentzelia nuda (Loasaceae) in Nebraska Sandhills prairie. American Journal of Botany 74(6):785-791. Retrieved from https://www.jstor.org/stable/2443859

Lesica, P., Lavin, M. & Stickney, P.F. (2012). Manual of Montana vascular plants. Fort Worth, TX: BRIT Press. 

Schenk, J.J. (2013). Evolution of limited seed dispersal ability on gypsum islands. American Journal of Botany 100(9):1811-1822. Retrieved from https://bsapubs.onlinelibrary.wiley.com/doi/pdfdirect/10.3732/ajb.1300075

The post Fly killer, bee lover: the secret life of Mentzelia decapetala appeared first on Wild With Nature.

July 27, 2022

She’s fuzzy and yellow, the size of my thumb. The pollen basket on her hind leg holds an orange loaf as she moves methodically from flower to flower. She forces her head down inside a greenish-white Canada milkvetch bloom (Astragalus canadensis), then wiggles onwards to the one above it. We can see at least three bumblebees working this milkvetch patch right now, down here among the sapling willows along the creek. 

I’m here this morning with my friends Greta and Augie Dobrecevich, hoping to learn something from the bumblebees. These large, fuzzy pollinators are easy to notice. They’re also fairly straightforward to identify in the field, without having to collect them. Besides, I’ve talked with a few Helena-area folks recently who have commented on how few bumblebees they’ve seen this spring. All of this adds up to an interesting start for a day in the field. 

How many bumblebees can we find today? What flowers are they visiting? And what can they teach us about this landscape?

It’s already hot this morning. The air is still. The distant mountains are a smoky blue from far-off fires. Once in a great while, a meadowlark sings. Most of our early summer birdsong has already dried up. We’re entering the quiet at the peak of summer. It’s the season of grasshoppers and young birds. It’s the season of flowering sweet clover, nodding thistle, and wild licorice. Is it the season for bumblebees, too? Today we’re hoping to find out.

An intro to bumblebees

Bumblebees are generalist pollinators – which means that just about any type of flower is fair game in our search. But they definitely do have preferences. Some species have long tongues to reach deep inside tubular flowers. Others have short tongues, useful for more-accessible blooms. In the past, I’ve found some species very frequently on plants in the pea family (Fabaceae), such as wild licorice. Others seem to adore thistles. And some flowers, like prostrate vervain (Verbena bracteata), a tiny-flowered native mat-former, seem completely uninteresting to our bumblebees.

Today our field gear is simple. We each have an insect net and a pocket full of plastic vials with snap-on lids. When we find bumblebees on flowers, we’ll try to net them and then transfer each one to a vial. In the shade, we’ve set up a cooler full of ice. We’ll place the not-very-happy bumblebees, in their vials, in the cooler to chill down. Once they stop buzzing around, we’ll be able to remove them and identify them. Then, we’ll let them warm up again and fly off. A cool bumblebee is amazingly docile. They’ll cling gently to a finger as they buzz their wings and raise their body temperature to flight range. I’ve never had a bumblebee try to sting me as it is warming up.

Important note: if you try this at home, make sure to use a cooler with ice or a refrigerator to chill the bees. Freezers are way too cold – they will kill bumblebees, not chill them.

For identification, I am using an excellent Forest Service guide, Bumble Bees of the Western United States. I’m supplementing this guide with an updated identification key created by Montana State University. This key covers female bumblebees of all species known or expected in Montana.

Buzzing in the milkvetch

I’m still watching the same bumblebee in the Canada milkvetch. I raise the net, gauge the distance to her flower, and swing. She tumbles in and begins buzzing ferociously, clearly not happy about this interruption to her breakfast. A pungent smell wafts up from the unhappy bee. To me, it smells exactly like a honey and lemon toddy. I maneuver a vial into the net and ease her in. 

Though it’s early in the day, it’s already clear that the Canada milkvetch is a great bumblebee plant. It’s not long before we have a handful of them in vials, buzzing their displeasure. I carry them up to the cooler, where I check on the first bumblebee of the morning. Augie found this one right as we were starting out, visiting small tumble-mustard (Sisymbrium loeselii) in an area of disturbed soil near where we parked. She’s smaller than the bees on the milkvetch, with a striking band of orange hairs across her abdomen. And she’s already cooled down enough for photos.

Using a 10x lens for magnification, I examine her. She has a moderately long cheek. Funny enough, cheek length is often a critical characteristic to look for when identifying bumblebees. Besides the conspicuous orange hairs on her abdomen, she also has a black stripe across her thorax, sandwiched by yellow. She’s a Hunt’s bumblebee (Bombus huntii), one of the species I see very commonly around Helena. 

She crawls onto my finger and begins to warm up, shaking her wings and buzzing slightly. She moves to my fingertip, preens, and bobs her abdomen up and down. And then she flies off.

Some flowers are tastier

It’s not just interesting to see which flowers the bumblebees are visiting. It’s also interesting to see which ones they aren’t visiting. On my way back to the milkvetch, I stop to check a patch of Canada goldenrod (Solidago canadensis). It’s recently come into bloom, an incredible array of deep, dazzling yellow. And it’s buzzing with pollinators. There are black wasps, yellow-and-black wasps, white-striped wasps, and green wasps. I see a fuzzy orange bee fly on the flowers. But I don’t see a single bumblebee.

I stop to check in with Greta, who is watching a tangle of white clematis (Clematis ligusticifolia). There are wasps visiting these flowers, but no bumblebees here, either.

I’m starting to get a sense of how this landscape might look through bumblebee eyes. It’s not just a pretty tapestry of grasses, shrubs, and flowers. There are lots of resources here for a bumblebee in search of pollen and nectar, but they’re patchy. They’re few and far between. From a bumblebee’s perspective, this landscape must look like a map of flower patches. Canada milkvetch, it seems, is highlighted on this map. Meanwhile, white clematis and goldenrod don’t even show up. And these flower patches exist in a sea of mostly uninteresting grasses, connected by a bumblebee’s memory and flight. 

Flies in the snowberry patch

Now I’m standing in a thick patch of western snowberry (Symphoricarpos occidentalis). I’ve seen bumblebees visiting snowberry flowers before, so I’m hoping I’ll find some here today. Surely they must be here, I think, among all of these sweet-scented, light pink bells. But so far, I’m not seeing any. Instead of the powerful, insistent buzz of the bumblebees, I’m hearing a higher-pitched, soft buzz. The sound is coming from several hairy black flies, as large as a bumblebee, with a dab of orange near their wing bases. These are tachinid flies (family Tachinidae), a group of parasitoids as strange as the ichneumonid wasps I looked at last month. Tachinid flies are very diverse, and many of them are quite colorful. In general, they tend to be medium or large, hairy, and extremely active. These large black ones are likely members of the genus Tachina. Little is known about the biology of this genus, but several Tachina species parasitize cutworms.

I spend several more minutes circling the snowberry patch, watching carefully and listening for the roar of a bumblebee. But none appear. Today, at least, the snowberry is not on the bumblebees’ floral map.

The most popular flowers

I find myself back along the creek in another patch of Canada milkvetch. This one is still in full bloom, and the bumblebee activity here is incredible. Immediately in front of me, five of these large, fuzzy pollinators are going from flower to flower. It’s a full-time job just netting them and putting them in vials. 

I find Greta across the creek; Augie is searching farther downstream. As we cross back over to finish searching the milkvetch patch, we hear a distinctive whistle of wings. It’s a mourning dove, flushing from a chokecherry thicket past our shoulders. We turn around to look. There among the branches, in the cover of a white clematis vine, is a mourning dove nest. Two half-grown nestlings, covered with pin feathers, are looking back at us from the haphazard platform.

We leave the mourning dove chicks in peace and return to the milkvetch patch. The bee diversity is both exciting and overwhelming. There are dozens of bumblebees, with at least three species here. We watch them, swing nets, and transfer massive, grumpy bees into vials. 

It’s time for a break: we’ve filled all of the vials in our pockets with bees. We return to the cooler and compare notes. What Greta and Augie have seen matches with my observations: milkvetch seems to be the most popular flower by far. Augie mentions finding a few bumblebees on Rocky Mountain beeplant (Cleome serrulata), as well.

Identifying bumblebees

Now it’s time to identify the bumblebees from earlier. We take them out one by one. As with the Hunt’s bumblebee I already released, we’re looking at general pattern, coloration, and cheek length. All of these bees are pollen-collecting females. We can see the shiny, concave pollen baskets on their hind legs. 

We have to work fast. Soon after we remove a bumblebee from the cooler, she begins to move, twitching a leg. It doesn’t take long before she stretches her legs and begins to crawl. It’s absolutely endearing – but it means that identification has to happen fast. It’s very hard to examine a bumblebee’s cheek under magnification when she’s crawling around and preparing for takeoff.

This one is a white-shouldered bumblebee (Bombus appositus). She has a strikingly white band of hairs across the front of her thorax, and her abdomen is mostly yellow. After I get done identifying her, I hold her on my finger. She twitches her legs and bends her abdomen down, buzzing it slightly. We transfer her to Greta’s finger and she clambers aboard, allowing us to admire her intricate fuzziness. And then, without warning, she takes off, buzzing heavily away.

Preference and bias

We talk about the patterns we’re seeing. Clearly the bumblebees are loving the milkvetch today. We’ve seen dozens of them visiting it. On other plants, the bumblebee attention has been sparse. So far we’ve just spotted a few on the small tumble-mustard and a few on the Rocky Mountain beeplant.

That’s been it. We’ve been checking other flowers, too: snowberry, goldenrod, clematis. We’ve been trying to check as many different plants as possible. We know that if we assume that milkvetch is attractive and neglect other flowers, its attractiveness may reflect our bias rather than a real pattern. But so far, we haven’t found any other flower patches that can compare in terms of bumblebee interest.

Most bumblebees have a long flight season, much longer than the flowering period of a single plant. So when we think about bumblebee habitat on this landscape, we have to remember that it’s not just about what we see today. It’s very possible that I might have seen bees from these same colonies visiting the two-groove milkvetch (Astragalus bisulcatus) here a month ago. In another month, they may be choosing between Rocky Mountain beeplant, white sweetclover (Melilotus alba), and Nuttall’s sunflower (Helianthus nuttallii) along this stream. If we want to encourage bumblebees, we need to think about a full season of attractive flowers for them.

We’re reaching the end of the morning, and Greta and Augie have to leave. All of the bees we just caught on the milkvetch are cooling down. I decide to do one more foray, going farther afield and specifically looking for floral diversity. Besides the milkvetch, what else are the bumblebees visiting today?

Dryland flowers

I walk out into the dry grassland away from the stream. Here and there, I spot a clump of alfalfa (Medicago sativa), bearing a mixture of deep purple blooms and developing fruits. The hairy goldenaster (Heterotheca villosa) is a patchwork of bright yellow flowers and tawny seed tufts. I do notice a few bees visiting it, but these are smaller species with less hair. The buzzing of bumblebees is nowhere to be heard.

There’s a large patch of Russian knapweed (Acroptilon repens) in a swale running through the grassland. It’s a lumpy, bushy expanse of green, pink, and white in the hot midday breeze. I’m not seeing bumblebees here yet, but this patch is bobbing with activity. There are a few honeybees and the occasional, golden-haired bee fly. But the most noticeable thing is all of the nectaring butterflies. There are checkered whites (Pontia protodice), common wood nymphs (Cercyonis pegala), clouded sulphurs (Colias philodice), and a few blues. They dance nimbly, landing on the flowers and fluttering upwards again. 

Dryland bumblebees

And then I spot a small bumblebee, moving from flower to flower. I inch the net closer. It’s trickier to catch bumblebees in the Russian knapweed than it was in the Canada milkvetch. The stems are stiff and the foliage is dense. I sweep. The bumblebee tumbles into the net. 

The bumblebee abundance here is still nowhere near what we saw on the milkvetch earlier this morning. But still, it’s clear that this patch is on their foraging map. Within a few minutes, I catch five of them – all relatively small, fuzzy worker bees. 

I notice elongate, sausage-like swellings along some of the Russian knapweed stems. These are galls formed by the larvae of the Russian knapweed gall wasp (Aulacidea acroptilonica), a tiny biocontrol insect that reduces the seed production of this non-native plant. These wasps seem to be well-established in this patch.

Farther along the swale, I find another rank, yellow patch of small tumble-mustard (Sisymbrium loeselii). Several bees are visiting these flowers, including another small bumblebee.

A hot breeze is blowing as I walk across the grassland. Thunderheads are building over the mountains. I continue searching, crossing expanses of dry grasses without any flowers at this season. These areas must seem desolate to a bumblebee. I’m probably walking past some bumblebee nests, though. These fuzzy insects are usually ground-nesters, often reusing a rodent burrow for their small colonies.

Knapweed and toadflax

I cross the creek again and find myself on a dry hillside, in an extensive patch of yellow and pale purple. It’s a mixed stand of spotted knapweed (Centaurea stoebe) and dalmatian toadflax (Linaria dalmatica). I know what people think about these plants. They’re among our most hated weeds, both on the Montana noxious weeds list. But today, I’m wondering what the bumblebees think of these plants.

Right away, I find a large female visiting the toadflax. She goes from blossom to blossom, dipping her head inside. I can hear several others in the vicinity. They’re skittish, visiting a few flowers and then departing in a long-distance flight. Nevertheless, I manage to net several of them. From a bumblebee’s perspective, the toadflax appears to be of some interest. It’s not anywhere near as popular as the Canada milkvetch, but it’s definitely more interesting than goldenrod or clematis. 

What about the licorice?

My pocket is full of bumblebees now. I only have one empty vial left. But there’s one more plant I’d like to check today. It’s wild licorice (Glycyrrhiza lepidota), growing down along the stream. Like Canada milkvetch, this robust native plant is in the pea family (Fabaceae). It’s passed peak flowering by now. Many of the once-white flowers have dried up already. In their place, the poky green fruits are swelling up. Once they ripen, they’ll act like peapods with burs, catching on passing animals and dispersing to new locations. 

Even though most of the licorice flowers are fading, right away I find several more small bumblebees, gathering the last bits of the season’s sustenance from this patch. With their rusty-banded abdomens, they all appear to be Hunt’s bumblebees. I watch one of them for a while as she moves diligently from flower to flower. Then I net her.

In other years, when the wild licorice has been at peak bloom, I’ve noticed that it seems almost as popular as the Canada milkvetch. At these times, the licorice has been teeming with bumblebees. Today it’s not quite that exciting. Except for these few rusty-banded females, the bumblebees have turned their attention elsewhere. It’s another illustration of seasonality: even a few weeks can make a big difference in terms of flower popularity.

I know that there must be more bees out here today, but I’m ready to wrap up my observations. We’ve netted 35 bumblebees today. Who are they all?

Patterns in the bumblebees

I return to the cooler. It’s time to identify the remaining 30 bees. I pull them out one at a time, running them through the identification key. Gradually, some patterns emerge. On the Canada milkvetch, three species are common. As we’ve already seen, the white-shouldered bumblebees (Bombus appositus) are mostly yellow, with a striking white band across the thorax. Nevada bumblebees (Bombus nevadensis) often have a black dot between their wings, surrounded by yellow hairs. The third common species on the milkvetch is the golden northern bumblebee (Bombus fervidus), a bright yellow creature with a furry black dash across the thorax.

The strikingly orange-banded Hunt’s bumblebee (Bombus huntii) is a milkvetch visitor, too, but this species seems to be a true generalist. We’ve caught at least one of these on literally every single plant that we’ve found bumblebees on today.

Every one of the 35 bees we’ve caught today has been a female. This makes sense: male bumblebees are most common in the fall, when they’re searching for queens to mate with.

Bumblebees are social insects. This makes them like honeybees but unlike the vast majority of our other bee species. And while honeybees have massive, long-lived colonies with many workers, bumblebees start over again each year. Only the queens overwinter. In the spring, they forage and start new colonies, raising the first generation of worker bees. From then on, the queen stays home and the workers forage.

Queens vs. workers

Bumblebee queens are massive, while the workers tend to be smaller. Most of the bees we’ve found on the Canada milkvetch are huge – so these seem to be queens that are still raising their first-generation workers. In comparison, the Hunt’s bumblebees we’re seeing are diminutive. These are almost certainly workers. The Hunt’s bumblebee queens were visiting flowers earlier in the season. Now they’re staying home, laying more eggs.

The Rocky Mountain beeplant (Cleome serrulata) yields an interesting bee. Like all of our bumblebees today, this is a female, with 12 antennal segments (males have 13). But the hind tibiae of this one are entirely hairy. There’s no shiny, concave pollen basket. Why?

This one looks like a bumblebee – but it’s not! (This one had me fooled. Dr. Casey Delphia, a bee biologist from Montana State University, had to correct me on it.) Instead, this hairy bee is in the genus Anthophora, a large group of bees that generally nest in the ground. Unlike bumblebees, Anthophora females tend their nests on their own, without help from workers – though females of some Anthophora species will share a single entrance hole to their nests.

Different bees on the knapweed

When I switch to the Russian knapweed vials, things really start to get interesting. The first of these bees is a small female with pollen in her baskets. She has orange on her abdomen, like the Hunt’s bumblebees. But the banding isn’t as precise. And looking at her face with my 10x lens, I can see that her cheek is very short. I also notice that the hairs on her face are black, while Hunt’s bumblebees have yellow hairs here. This is a red-belted bumblebee (Bombus rufocinctus). 

And she isn’t the only new species from the Russian knapweed patch. I’ve also caught several two form bumblebees (Bombus bifarius). These females are decked out in black and yellow stripes.

As I move on to the bees from dalmatian toadflax (Linaria dalmatica), I return to some familiar species from earlier. Nevada bumblebees and Hunt’s bumblebees are the common visitors on the toadflax today.

Some of the others aren’t so easy. Sometimes I struggle through the key, debating about whether a cheek is truly long or short. In the end, I’m left with just one bee that remains unknown. I take photos, jot down notes, and hope that some friendly bee expert will be able to help me figure it out later. 

One by one, the bees preen, warm up, and fly off. Finally, I finish identifying the last one. As I had suspected, this rusty-banded female from the wild licorice is another Hunt’s bumblebee.

Counting them up

Among these 35 bees, we’ve identified six species. Plus there’s still that one bee that has me stumped. We’ve learned something today about each of these species: what flowers they like, what flowers they don’t like, and how common they are here.

• Hunt’s bumblebee (Bombus huntii): 8 females. Seen visiting every flower where we found bumblebees today: Russian knapweed (Acroptilon repens), Canada milkvetch (Astragalus canadensis), spotted knapweed (Centaurea stoebe), Rocky Mountain beeplant (Cleome serrulata), wild licorice (Glycyrrhiza lepidota), dalmatian toadflax (Linaria dalmatica), and small tumble-mustard (Sisymbrium loeselii).
• White-shouldered bumblebee (Bombus appositus): 6 females. Only seen on Canada milkvetch (Astragalus canadensis).
• Golden northern bumblebee (Bombus fervidus): 5 females. Only seen on Canada milkvetch (Astragalus canadensis).
• Nevada bumblebee (Bombus nevadensis): 11 females. Seen on Canada milkvetch (Astragalus canadensis) and dalmatian todaflax (Linaria dalmatica).
• Red-belted bumblebee (Bombus rufocinctus): 2 females. Only seen on Russian knapweed (Acroptilon repens).
• Two form bumblebee (Bombus bifarius): 2 females. Only seen on Russian knapweed (Acroptilon repens).

It’s a start

I could spend hours more – no, days more – out here learning about this community. Eventually, I might be able to see this area like a bumblebee does: a four-dimensional patchwork of flowers coming in and out of season, some more interesting than others. There are so many more questions. Are there other bumblebee species here? What other flowers are attractive to them? With more time, I could watch the bees’ behavior and learn the dances they use to collect pollen and nectar.

But for today, I’m content with our foray. We’ve begun to learn which flowers the bumblebees like. We’ve gotten up close and personal with an abundance of bees, far more of them than I would have guessed we might find here. Maybe next summer we can do this again.

Learning from the bees

In the meanwhile, what are our takeaways? First, there are a lot of bumblebees out here. And when we take the time to really look for them, they have so much to teach us. Second, Canada milkvetch is a really popular plant right now for bumblebees. But that won’t last forever: the milkvetch flowers will fade, and the bees will have to look elsewhere for food. The milkvetch isn’t the answer for all of our bees, either. The red-belted bumblebees and the two form bumblebees showed no interest at all in it today. Instead, they visited Russian knapweed, another of those frequently-maligned plants on our state noxious weeds list. 

So if we want to support bumblebees, plants like Canada milkvetch can help. But one plant isn’t going to be enough: we’ll need attractive bumblebee flowers throughout the flight season. We’ll need plants with deep flowers, like the milkvetch, and plants with more-accessible blooms, like the knapweed. If we want bumblebees, we need plant diversity.

In terms of personality, bumblebees remind me of bears. They’re fuzzy, they’re remarkably photogenic, and they go about their business in a charming, bumbling way. After today, I definitely want to see more of them around. So when it comes to planting Canada milkvetch around Helena, sign me up.

Further Reading

Wilson, J.S. & Carril, O.M. (2016). The bees in your backyard: a guide to North America’s bees. Princeton, NJ: Princeton University Press.

The post Bumblebees of Helena: getting to know our fuzzy neighbors appeared first on Wild With Nature.

July 21, 2022

I first notice the scent from 40 yards away, subtle but powerful. The milkweed is fragrant, almost like carnations. I’m at the edge of the largest patch of showy milkweed (Asclepias speciosa) that I know of around Helena. The robust stems grow up tall out of the smooth brome along the canal. On the other side, traffic rushes past along York Road. I’m at West Mont Farm and Gardens, where I’ve gotten permission to look for insects on the milkweed this morning. And there’s one insect I’m especially hoping to find: the monarch butterfly. 

The migration of monarchs is a story so well-known that it falls easily into clichés.

The epic migration of a half-gram insect. For years, the story of the monarchs was just an abstract concept to me. Did we even have monarchs in Montana? From time to time, I would ask a biologist. They were rare here, it seemed. Maybe they were just migrants. Did they ever breed here? Maybe in eastern Montana. Maybe once in a great while.

Not quite so rare

Then I met Laura Alvey, who lives at the edge of the Helena Valley, where the land rises up into the granitic mass of the Scratchgravel Hills. Her yard is an oasis of native plants that she has planted and tended over the years. Showy milkweed (Asclepias speciosa) grows exuberantly there. And I was thrilled to learn that Laura has not only seen monarchs here – they have also laid eggs on her milkweed! She has gotten closely familiar with these butterflies. With her children, she’s raised several of the caterpillars to adulthood, providing them a safe home through the larval stage and then releasing the adults to continue their journeys.

The conversation with Laura was my first clue that monarchs are an important part of the Montana landscape. And then last winter, I learned about the monarch studies Maggie Hirschauer and a team of volunteers were doing in western Montana’s Bitterroot Valley, from Missoula to Stevensville. From 2019 to 2021, they found 41 wild monarch eggs and larvae in that valley. So do monarchs breed in Montana? Yes! And not just one or two of them. It was at this point that I knew I wanted to take a closer look around Helena. If they could survive in Laura Alvey’s yard, surely there might be other patches, too?

The danger of extinction

But today, a shadow hangs over this long-awaited monarch search. As I scanned my news feed before I came out here this morning, I read that our monarchs (Danaus plexippus plexippus) had just been listed as Endangered by the IUCN. This is a non-regulatory ranking put out by an international, highly respected group of scientists. An IUCN Endangered listing is a major cause for alarm, but it’s not regulatory: unlike the Endangered Species Act, it doesn’t impose legal obligations.

In the case of our native monarchs, there is major cause for alarm. In the past three decades, monarch populations overwintering in California have shrunk by over 99 percent. From nearly 10 million in the 1980s, they’ve crashed so hard that now there are less than two thousand of them left. More monarchs still overwinter in Mexico, but the Mexican population has declined by 84 percent since the 1990s. In short, our migrating monarchs are at risk of extinction. 

This is grim news, but it makes today’s search even more timely. Are there still monarchs in the Helena Valley? If they’re anywhere in this valley, it seems like they might be here, in West Mont’s extensive milkweed patch. The milkweed extends for over a hundred yards, a forest of velvety green leaves and pink flower umbels. Between York Road and the farm itself, it’s a luxurious milkweed thicket, growing alongside the irrigation canal and two smaller ditches. I have no idea if I’ll actually find monarchs today. But monarchs or not, I’m hoping I’ll learn something about milkweed and the creatures it sustains.

The trapped honeybee

Right now I’m sitting at the edge of the patch, taking a close look at the milkweed flowers. Hundreds of honeybees are flying from one flower to the next. I can barely hear their buzzing over the steady rush of the irrigation pump nearby.

I spot a honeybee struggling wildly on a milkweed flower. Its hind leg is caught. The bee is fluttering desperately to get free. This is something I’ve read about in Milkweed, Monarchs, and More, a delightful field guide that has helped introduce me to the milkweed community. It turns out that this stuck honeybee can teach us a lot about milkweed flowers and how they get pollinated.

How milkweed gets pollinated

The flowers are striking: works of evolutionary architecture as intricate and weird as those of leafy spurge. At peak bloom, the milkweed petals are a striking carnation-pink, each with crisp white edging. The petals bend backwards, accentuating five intricate white horns that protrude from the center. Each horn has a cup at its base, and each cup holds nectar. Meanwhile, between the horns there’s something that looks like a greenish-white barrel.

This barrel holds the pollen and the incipient milkweed fruit – but it’s also a trap. Along its edges are five vertical slits. Each slit holds pollen, neatly wrapped up into tidy, elongate packets. From time to time, as a bee or a fly gathers nectar, its leg will fall into one of these slits. And as the insect struggles to free its leg, it picks up a pollen packet.

This honeybee has a leg stuck in the pollen barrel. As she tries to get away, I can see the yellow pollen packet dangling from her foot. She keeps buzzing her wings, but her leg remains stuck. Finally, after a minute or so, just as I’m about to help her, she struggles free and flies off, carrying the pollen towards the next flower cluster.

But this bee seems to be the exception rather than the rule. I watch dozens of others deftly sticking their heads into the milkweed horns, gathering nectar, and moving to the next horn. Apparently, the nectar is good enough that it outweighs the small risk of getting stuck.

Ants and milkweed bugs

Besides the honeybees, there are lots of ants here, each one black with a reddish thorax. Like the honeybees, they’re busy crawling into the milkweed horns, gathering nectar.

According to Milkweed, Monarchs, and More, ants take nectar from milkweed without contributing to pollination. But apparently Montana’s ants don’t know that. I watch one vaulting from horn to horn, a yellow pollen packet trailing awkwardly from its middle leg. 

Nearby, I catch sight of a small milkweed bug (Lygaeus kalmii). It’s as striking as the milkweed flowers themselves, a portrait in red, gray, and black. These bugs are less commonly-known than monarchs, but they are also a characteristic part of the milkweed community. And they’re important to the interactions that go on here: not only do they feed on milkweed foliage and seeds, but they also scavenge dead insects. Sometimes they even attack monarch larvae. Earlier in the spring, they may also feed on other plants nearby.

I still haven’t moved from the spot where I’m sitting, by the pump. From this vantage point, the milkweed patch really does look like a forest. The thick stems and broad leaves arch skywards, carrying the pink flower clusters.

Beginning the search

The West Mont Farm manager, Jeremiah, tells me that he’s already seen a few monarchs this year, elsewhere in the Helena Valley. Have they visited this patch, too? Monarch females can lay up to 400 eggs. Typically, they lay each one singly, hidden on the underside of a milkweed leaf. There are thousands and thousands of leaves here. It’s time to start looking!

Now I begin to search the velvety leaves for monarchs. I check the undersides for eggs, look for larvae, and watch for signs of feeding. It’s a daunting, massive task. I keep getting distracted as my eyes gravitate to the honeybees on the flowers. Ten leaves in, I spot a daddy long-legs (order Opiliones), one of those familiar spider-relatives that scavenge and hunt small insects. After a dozen more leaves, I find a tiny spider nestled in an inconspicuous web. It’s hidden in a fold near a leaf tip.

My eyes wander back to the milkweed flowers. We have blooms of all stages here, from unopened buds to pink and white umbels at the peak of flowering. The horns grow creamy as the flowers fade. There are already a few fruits developing, still no larger than an almond. 

Okay, back to leaf-searching. There’s a greenish grasshopper nymph resting low on the milkweed, missing a hind leg. Near it, half of a leaf has been chewed away. Nearby, I spot another grasshopper. This is an adult two-striped grasshopper (Melanoplus bivittatus). Strangely, this one is also missing a hind leg, plus part of an antenna. Did both grasshoppers manage narrow escapes from a spider, or from some other predator?

Other butterflies and their eggs

I notice a small white blob under a milkweed leaf. Is it a monarch egg? No, it lacks the fine sculpturing. And there’s a faint white trail where it rolled down the leaf: it’s a blob of dry milkweed sap.

Then I spot a flash of movement: there’s a butterfly on the milkweed flowers! It’s a big one, but it’s not a monarch. Instead, it’s a western tiger swallowtail (Papilio rutulus), and it’s very interested in these flowers. Normally I see tiger swallowtails in flight, ignoring flowers and floating powerfully past on strong wingbeats. But this one is avidly nectaring, unfurling its proboscis at flower after flower and probing the milkweed horns for sugars.

Why am I so easily distracted from my leaf search? If only I could find an adult monarch here, this whole process would be so much easier! This spring, on May 4, that was exactly the experience I had with a Milbert’s tortoiseshell butterfly (Aglais milberti). I noticed an adult along a stream, resting upside down on a stinging nettle leaf (Urtica dioica). Knowing that stinging nettle is the larval host plant for this species, I watched carefully. The butterfly rested for a long time on the leaf, then flew away as I inched closer. And there, well-hidden on the underside of the leaf, I found a cluster of 11 barrel-shaped eggs. If only the monarchs would be so obliging…

Monarchs and viceroys

And then, right after I have that thought, I see a monarch. At least, I think it’s a monarch. I still need to see it land and get a better look. Besides monarchs, we also have viceroys (Limenitis archippus) around here – and these butterflies do a great job of mimicking monarchs. But although these species look so similar, their life cycles are incredibly different. Our monarch larvae depend on milkweeds (Asclepias spp.) and are obligate migrants. The only way these butterflies reach Montana is by a long migration from overwintering sites in Mexico or California. Viceroys, on the other hand, do not migrate. Their larvae feed on willows (Salix spp.). And somehow, these larvae survive the Montana winter hanging from a willow, wrapped in a dead leaf. 

The large orange butterfly is circling warily. I stop breathing. It lands on a flower for the briefest of instants, then reconsiders. Leaping back into the air, it circles around me. I try not to make any movement. It flutters rapidly eastbound. I follow at a discreet distance. Now it’s landed again, and this time it’s probing the milkweed horns with its proboscis. 

I raise my binoculars, then the camera. Yes! The hindwing is a clean, black-veined orange, without the interrupting black bar that identifies a viceroy. It’s a monarch in the milkweeds! This is pretty special.

Two special butterflies

For that matter, viceroys are pretty special, too. From what I’ve seen so far, both species seem to be fairly rare around Helena. Last week, on July 16, I was leading a bird walk at the Upper Prickly Pear Fishing Access Site. As I casually checked a patch of flowering milkweed there for monarch larvae, I saw a large orange butterfly in flight. A monarch? This one was not. When it landed, I was able to see the interrupting black bar cutting through the hindwing. It was a viceroy. And in nearly six years of living in Helena, this is only the second viceroy I’ve ever seen. But are these butterflies actually rare here, or do I just need to look harder? I’d love to hear about your observations in this area: either viceroys or monarchs! If you’ve seen them, please leave a comment!

Distracted by beetles

The monarch is flighty, spending only a short time on one flower cluster before moving on to the next. And it’s only nectaring – I don’t see any sign of egg-laying behavior this morning. And no wonder: when it spreads its wings, I see a small black spot in the middle of the hindwing. Only male monarchs have this spot. This one won’t be laying eggs.

Still, a monarch is here! And if one is visiting, hopefully others are too. It’s time to redouble the egg search.

But first, I find another excellent distraction. There’s a pair of striking red beetles mating on a milkweed flower. These are milkweed longhorn beetles (Tetraopes sp.). And like monarchs and the small milkweed bug, Tetraopes are characteristic milkweed associates. The larvae feed underground on milkweed roots, while the adults chew on the foliage. After mating, they’ll lay their eggs at the base of a milkweed stem, completing their life cycle.

Several other Tetraopes are crawling on milkweed leaves nearby. I notice that several of these leaves have the tips cleanly cut off in a half-circle: a classic feeding sign left by these beetles.

Searching through the milkweed

I’m completely daunted by the prospects of finding a monarch egg, or a tiny larva, among all of these leaves. But if I don’t look, I definitely won’t find anything. I decide that I’ll give myself an hour to do a careful search. I’ll check leaf undersides, look for leaves with feeding damage, and keep my eyes open for adult monarchs. And for this hour, I’ll try not to get so distracted.

It’s not quite noon yet, but the day is already hot. A blustery west breeze has picked up. I decide to focus on the area where the milkweed is especially extensive. The male monarch was nectaring here – so maybe females favor similar areas. Ready, go!

There’s something rather calming about pushing back the soft milkweed leaves, looking for butterfly eggs. If it weren’t for the occasional mosquito whining in my ear, this would be very relaxing. Although the mosquitoes aren’t the only problem. Among this forest of milkweed, I haven’t found a single monarch egg. They must be here, I keep telling myself. I start to suspect that there’s something wrong with my searching technique. Maybe I’m overlooking them. May I’ve already skimmed past dozens of monarch eggs!

Now I’m 24 minutes in, and I’m beginning to feel pretty silly. I’ve checked hundreds of milkweed leaves. No eggs. Nothing. 

Hiding in plain sight

Then I look up, and my heart stops. There’s a lone milkweed plant at the edge of the patch, and among its flower buds is a caterpillar. It’s clearly a monarch, strikingly obvious among the buds, boldly banded in white, black, and yellow. It’s almost two inches long, far past the stage at which young monarch larvae try to hide. Its message to predators is clear: I taste bad! Don’t eat me!

The caterpillar rests, quiescent. Below it, a quarter of a young milkweed leaf is gone. Presumably this is where the caterpillar started its life. At least one of them is here! And where there’s one, there might be hundreds more.

I continue the search, alternating between a quick, general look for older caterpillars and careful leaf observation in search of eggs. From time to time, I see leaves with signs of feeding, but I have no idea if these signs are from monarchs or from some other creature. Each time, I check the surroundings for caterpillars, but I find none.

The pollinators of milkweed

I haven’t seen any more adult monarchs since I spotted the nectar-seeking male, hours ago. As I walk in search of monarchs, I’m still noticing the flower visitors. There are hundreds upon hundreds of honeybees. They and the ants are by far the most abundant insects on these flowers. I find one dead honeybee, its leg still trapped in a pollen barrel, another leg clinging to a packet of pollen. This one wasn’t able to get free. Besides the honeybees, I spot a yellow-haired bee fly and a few other flies. A single bumble bee (Bombus sp.) is visiting the blooms. But the diversity of flower visitors today is surprisingly low, much lower than what I saw on leafy spurge last month.

Why, I wonder? Why is it that ants and a non-native bee are the only common pollinators on this nectar-rich native plant? In the past, I’ve casually noticed several wasp species visiting milkweed flowers. But I’m not seeing them today, nor am I seeing other types of bees. I wonder if this might be a reflection of the broader landscape. This part of the valley is a mix of housing developments and agriculture. Native plants seem few and far between. Could it be that other pollinators are missing important resources that they need? What if we provided a greater diversity of flowering plants? If we left areas of bare soil for ground-nesting species and dead twigs for stem-nesting bees, would we find more pollinators on the milkweed? Or is milkweed just not very attractive to many of our flower-feeding insects?

Leaving with questions

I check a few more milkweed plants, searching the leaf undersides. I notice a few ladybugs, a couple of seven-spots and a couple of transverse ladybugs. These are the species I found so commonly on the sagebrush last week.

The sun is overhead now. My hour is up. After seeing the single caterpillar, I haven’t found any more monarchs.

Are there more of them here? Among the complexity of this milkweed forest, it’s easy to imagine them hiding, eggs or tiny larvae within this sea of leaves. Perhaps I can come back in a few weeks and look again. Or maybe that’s all this year: one monarch from Helena’s milkweed stands. With luck, it will avoid the small milkweed bugs. I hope it will pupate successfully and flutter skywards next month, bound for a destination that only it knows.

It’s not clear where Montana’s monarchs go. In her work in the Bitterroot Valley, Maggie Hirschauer has observed wild, captive-reared adults orienting mostly to the east and southeast when they are released. This suggests that they aren’t bound for California. And in a 2005 article, Hugh Dingle and other researchers suggested that monarchs in our area likely migrate southwards to Mexico, finding their way along river corridors.

From our milkweed to Michoacán

After spending a morning here, this milkweed patch has found a special place in my heart. Where else but in a patch like this can we find milkweed longhorn beetles and small milkweed bugs? Where else can we watch honeybees, ants, and swallowtails sipping nectar from incredible blooms that smell like carnations, sometimes getting stuck in the pollen barrel?

In a moving video, Will Smith tells of how the monarchs arrive in Michoacán, Mexico every year, just in time for the Día de los Muertos (Day of the Dead). People see them as the souls of the dead, returning in celebration of family and connection. It’s not clear yet whether our Montana monarchs are among those returning to Michoacán. And if they are, it’s still harder to imagine their journey. But I like to try.

This November, imagine this caterpillar in its winged reincarnation, gliding over the streets of Michoacán and feeding on nectar from the golden cempasúchiles that decorate the graves of the dead.

To return from the dead

For a monarch to arrive in Michoacán, so many things must go well. There must be healthy milkweed populations all the way from Canada to Mexico. The caterpillars must avoid predators and drought. The adults must fly thousands of miles, avoiding wildfires and wind turbines, and they must have intact forests there for overwintering.

It’s overwhelming for any one person to even imagine. And as monarchs join so many other creatures on the IUCN Red List of Endangered life, it may seem like there’s not much that each of us can do.

But there is something we can do. We can care for our local milkweed and watch it for monarchs. (The Western Monarch Milkweed Mapper project provides one way to submit monarch sightings. Journey North provides another.) We can celebrate that we have milkweed patches as extensive and healthy as West Mont’s. And maybe we can start some new patches.

From seed, it takes a few years for milkweed plants to flower. Buried shallowly in potting soil and kept well-watered, I’ve found that the seeds take about a month to germinate. Right now, outside my door, there’s a planter filled with milkweed seedlings I started this spring.

I don’t know if I’ll ever have a patch as big as West Mont’s. But in a few years, if monarchs haven’t gone extinct, I hope to walk out into my yard and find one laying eggs on my milkweed patch.

And in the meanwhile, I’ll be hoping that somewhere out here, in this valley, we have more than just one monarch caterpillar, growing up in a forest of milkweed.

Further reading

Mahr, S. (no date). Common milkweed insects. Wisconsin Horticulture – Extension. https://hort.extension.wisc.edu/articles/common-milkweed-insects/

Rea, B., Oberhauser, K., & Quinn, M.A. (2010). Milkweed, monarchs, and more: a field guide to the invertebrate community in the milkweed patch. Union, WV: Bas Relief, LLC.

The post Creatures in the milkweed: searching for Montana’s monarchs appeared first on Wild With Nature.

June 23, 2022

Last week I found a surprising diversity of pollinators feeding on leafy spurge, a flower that everyone hates. But I also noticed a very different community of pollinators on the nearby two-groove milkvetch (Astragalus bisulcatus). This is a beautiful native plant, a flower that’s easy to like.

Today, in celebration of Pollinator Week, I’ve returned to pay close attention to the two-groove milkvetch and the insects it is supporting. Which insects are visiting the milkvetch flowers? What are they doing? And together with last week’s investigation of leafy spurge, what can this teach us about supporting pollinator diversity?

Symphony on the milkvetch

On this warm, sunny morning, the milkvetch patch sounds like a symphony of chainsaws. Dozens of honeybees (Apis mellifera) are working the long purple flower clusters. Every short flight they make is accompanied by a whining buzz. There are leafcutter bees here, too, about the same size as the honeybees and making similar-pitched buzzes. They’re easy to pick out, though. The leafcutters (family Megachilidae) have the undersides of their abdomens covered in bright golden-orange pollen. Leafcutter bees are the only group to carry pollen like this. All other bees gather pollen on their legs (except for a few that carry pollen internally, in their crop).

A few bumblebees (Bombus spp.) are stopping here this morning, too. They’re the basses of this symphony. One is lifting off right now, its wings giving a low, deep-throated roar.

Pollen dance

One of the leafcutter bees lands on a milkvetch flower. I inch closer until she’s just inches from my face. She pokes her head adeptly between the lower, canoe-like keel petal and the upper, purple-striped banner, forcing them apart. The keel contains the milkvetch anthers, with their bright red-orange packets of pollen. Between the anthers is the female part of the flower, the pistil.

Now the leafcutter bee does a dance that looks complicated to me, though it must be routine for her. She combs backwards with her middle legs. At just the right moment, she engages her hind legs, rowing them backwards as well. With the leg dance, she transfers pollen to the underside of her abdomen. It all happens so fast, it’s hard to see how she’s doing it. Her abdomen is already densely covered with pollen, held there by special, branched hairs. Mission accomplished, the leafcutter revs her wings and helicopters over to the next flower.

What about the honeybees?

The honeybees are acting differently. First, they aren’t flying as much. Instead, they’re spending a lot of time crawling from one flower to the next. A honeybee lands on a flower in front of me and I watch her closely. Like the leafcutter bee, she butts her head between the keel and banner petals, opening the flower. But she doesn’t bother to comb pollen onto her legs. In fact, the pollen baskets on her hind legs are completely empty. She doesn’t seem interested in the milkvetch anthers at all. Instead, her attention is directed farther inside the flower, where the keel and banner petals meet. Is she getting nectar instead of pollen?

I remove a flower for closer investigation. Unlike these bees, I’m not a milkvetch expert. Instead of using their well-practiced petal-shove, I open up the flower by indelicately ripping off the banner petal. At the base of the keel petal, I notice two lobes where the lateral petals, the wings, join the keel. Is there nectar there? I don’t see any obvious glands, like the nectaries of the leafy spurge from last week. But clearly there’s something here that is attracting the honeybees’ attention. It isn’t pollen, so likely it’s nectar, even though I can’t spot it with ten-times magnification.

Ghosts among the milkvetch

Something that I love about spending a day watching flower pollination is how much I only glimpse. Just like the massive trout that gets away, it’s a sure sign that there’s more going on here than we can grasp. Right now, I spot a hawkmoth (family Sphingidae) visiting the milkvetch flowers six feet away from me. It’s the size of a bumblebee queen. Its flight is silent and its wings are partially transparent. I reach for my insect net. The hawkmoth spots the distant motion and shoots away, a silent and wary ghost. 

What species is this hawkmoth, and what’s its story? Unless I’m able to catch one for a closer look, I’ll never know. So I keep my eyes peeled, hoping to get another glimpse of “the one that got away.”

Some of these milkvetches have already been in bloom here for three weeks. Most of the flowers are a deep, royal purple, but some plants are a pale lavender and I even spot one with all-white flowers. There are buds still at the tips of the plants. Below them are the open flowers the bees are visiting. Still lower, green fruits are swelling like miniature, drooping peapods. It’s easy to see the two deep grooves running along each fruit, the field mark that gives this plant its common name. The grooves are light green, outlined by red ridges.

Of peas and selenium

For those of you who are gardeners, you’ll recognize many family resemblances between these milkvetches and garden peas. They have unusual two-lipped flowers, pod-like fruits, and compound leaves made up of many leaflets. And like garden peas, the milkvetches are legumes (family Fabaceae). Their root nodules harbor nitrogen-fixing bacteria, allowing these plants to obtain nitrogen from the atmosphere.

Two-groove milkvetch is chemically interesting for reasons besides nitrogen fixation. It often grows on soils rich in selenium. Humans and many other animals need this element at small concentrations, but at high concentrations it becomes toxic. Two-groove milkvetch is rather unusual when it comes to selenium: it can accumulate high levels of the element in its tissues. By using particular chemical pathways to store selenium in forms the plant can recognize and handle with care, it avoids the potential toxicity of this element. Why is this advantageous? There are a number of reasons: 

• Two-groove milkvetch can grow in selenium-rich soils, areas inhospitable to many species. 
• By storing selenium, these plants become much less palatable to herbivores such as grasshoppers and prairie dogs. (However, some specialized insects have co-evolved to tolerate high selenium levels and feed on these plants.)
• These plants can act as selenium pumps, boosting levels of this nutrient in the soil around them. This makes conditions even less hospitable for intolerant plants, giving milkvetch a competitive advantage.

What about pollinators? So far, studies have shown that bees don’t seem to discriminate between flowers of selenium-accumulators and non-accumulators. In two-groove milkvetch flowers, selenium concentrations are high, but there aren’t any studies on selenium concentrations in this plant’s nectar or pollen. And whether selenium from flowers may affect bees (either negatively or positively) remains unknown. (However, honey from bees in selenium-rich areas seems to contain amounts that are beneficial for human health.)

Aphid ranching

Moving on from the puzzle of selenium ecology, I spot a few ants crawling around the milkvetch flowers. They’re much less abundant than the ants I saw on the leafy spurge last week. And what are these ants doing, anyhow? They aren’t actually entering the flowers, just clambering past them and around them. Then I see why: between the flowers, several stems are covered with colonies of black aphids. The ants are associating with the aphids, presumably protecting them from predators.

The relationship between aphids and ants is well-known: while the aphids feed on their host plant, they excrete a sugary honeydew for ants. In exchange, the ants guard the aphid colonies. So while the ants on the leafy spurge were feeding on nectar that the plant offered freely, and probably transferring some pollen in the process, these ants seem to be stealing sugars from the milkvetch by way of aphid ranching. And it seems they aren’t contributing to pollination.

Aphid ranching has its risks, though – and here comes one of them now. It’s a transverse ladybug (Coccinella transversoguttata), one of our native aphid predators. The ladybug crawls methodically along a milkvetch leaf, then flies nimbly to a raceme of flowers. This flower cluster doesn’t have aphids, but it’s just a matter of time until this ladybug will find its juicy lunch.

Ladybug ecology

All of this crawling and flying is typical ladybug behavior. Aphid colonies are short-lived. It’s hard to predict where they may show up, so these ladybugs have become adept at finding them. This is one of the reasons why buying ladybugs for your garden is usually a waste of time: they’ll probably fly away. Buying these frequent fliers can be problematic for other reasons, too. One of the most commonly sold species is the convergent ladybug (Hippodamia convergens). Like the transverse ladybug, this species is another of our native aphid-eaters. But ladybug suppliers don’t rear these in captivity – they collect them by the billions from places where these ladybugs gather to overwinter. How does this mass-removal of ladybugs impact our wild populations? No one seems to know yet. 

We do know, though, that these releases are rarely effective. What’s more, shipping these ladybugs around the country can spread diseases and parasitoids. For aphid control, a better bet might be to create good habitat around your garden for ladybugs and other predators. What makes good ladybug habitat? Consider planting two-groove milkvetch and other native plants. These plants host their own species of aphids throughout the season and also provide pollen and nectar.

I’ve already spotted two more ladybugs on the milkvetch: another transverse ladybug and a native Hippodamia (H. quinquesignata or one of its close relatives). With good habitat – aphids and a diversity of native plants – ladybugs will probably fly to your garden on their own. In fact, you may attract not just ladybugs, but also other aphid predators such as syrphid flies.

Bees beware

What’s that reddish wasp doing over there, lurking on the grasses near the milkvetch flowers? It’s actually a fly, not a wasp! It’s a pretty good mimic, though, with its slender, wasplike orange abdomen. Bees beware: this is a thick-headed fly (family Conopidae), a sneaky parasitoid. This one seems to be a member of the genus Physocephala, a group I’ve collected here before. How do these flies make their living? A female will lay in wait where bees and wasps are active, attacking them on flowers or in flight. She will rapidly insert an egg into the hapless host’s body. If she succeeds, her larvae will feed inside the bee or wasp, eating it from the inside until it dies. It’s gruesome, but it’s also just part of the complex world of this milkvetch patch. Insects are stranger than science fiction!

A tiny, iridescent greenish-black bee is flying from flower to flower now. Its gentle buzzing is impossible to hear over the chainsaw symphony of the honeybees. I catch this one and see that its abdomen is covered in orange pollen. It’s another species of leafcutter bee! Then I spot a third leafcutter species, this one with a rusty-haired thorax and shiny black abdomen. The underside of its abdomen is just lightly dusted with pollen.

Windy afternoon

Throughout the morning, Helena’s usually-ferocious wind has been almost still. Now, as if it has realized its lapse, the wind has become a force to be reckoned with. Its gusts whoosh through the grasses, overpowering the buzzing of the bees. The bumblebees are nowhere in sight now. The milkvetch is bobbing so much that I can barely spot pollinators, let alone identify them. But still, the leafcutters and honeybees are holding on, climbing tenaciously into one flower after another. With such dedicated pollinators, it’s no wonder so many fruits are developing successfully.

Undoubtedly what I’ve seen this morning isn’t everything: there must be other pollinator species that visit the milkvetch. But for now, the wind is making further observations impossible. 

Yellow and purple

With the exception of the honeybees, none of today’s insects have overlapped with the pollinators I found visiting leafy spurge last week. And no wonder: these two flowers are as different as night and day. Yellow versus purple. Easy-to-reach nectar versus valuable pollen; slender wasps versus fuzzy bees. Both are flowering together here. And together, they’re supporting a much more diverse pollinator community than either could on its own. What if we could add more flower diversity here? If we added lots of other native plants – the flowers with which our pollinators have coevolved – how many more insects could we support?

The wind isn’t letting up. If anything, it’s getting stronger. With afternoon insect observations thwarted by the wind, I’m going to range farther afield and look for flower diversity. What other native plants can we find around here, flowering now or soon, that might add to the pollinator habitat in this grass-dominated patch?

Willow and beeplant

Along the edge of the stream is a slender, silvery-green stand of sandbar willow (Salix exigua). It, too, is flowering now, quietly offering up its inconspicuous, yellow catkins. I may get irritable with the wind, but the willows sway with it. (They whack me in the face as they do.) For insects, the leaves seem to be offering a bit of shelter from the gale. Even on this gusty afternoon, I spot a small, black bee on the flowers. This is a species I didn’t see on the milkvetch. The flowers are also sheltering several tiny flies and click beetles, feeding on pollen as they sway back and forth. Sandbar willows are a moisture-loving species, often growing right at the edge of streams and ponds. But irrigated lawns are a lot like floodplains: a small patch of sandbar willows could do well in a residential habitat.

In a bare patch, I find a Rocky Mountain beeplant (Cleome serrulata). This native annual will bloom from now until frost. In the afternoon’s wind, all I see on it are a few ants. But on other days, I’ve found bumblebees, small wasps, Becker’s white butterflies (Pontia beckerii), and many other insects on these flowers. Beeplant likes disturbed soil and is easy to grow from seed.

Globemallow, goldenaster, and thistle

Along a dry roadbed of dirt, away from the stream, I see a patch of scarlet globemallow (Sphaeralcea coccinea). This low-growing perennial is inconspicuous except when it flowers. Then, its broad red corollas catch our attention, as well as that of bees. Several bees specialize on globemallow flowers, including species of Perdita and Calliopsis.

Out in the arid grassland, a sea of yellow is blooming. It’s hairy goldenaster (Heterotheca villosa), another tough, low-growing perennial. These plants can keep blooming from now to the fall. And last September, I found a very special bee fly visiting these flowers. A grasshopper predator, Anastoechus barbatus lays its eggs on the soil. There, its larvae crawl along, searching for grasshopper eggs, which they destroy. I may think grasshoppers are cool – but anyone who’s ever had a garden devoured by them would probably beg to differ. This bee fly is a welcome addition to any garden – and so are the flowers that support it.

What’s that brush of light purple on the hillside? It’s our common, native wavy-leaved thistle (Cirsium undulatum). Sometimes people mistake it for one of our weedy, non-native thistles and kill it. That’s unfortunate, since these flowers host bumblebees and a range of other pollinators. Even in today’s wind, this single flowerhead holds 60 tiny gray beetles (probably soft-winged flower beetles, family Melyridae) and two large orange blister beetles.

And… more native flowers!

I’m having to search far and wide to find these flowers, but the diversity is a good sign for pollinators. In moister areas along the stream, I find yarrow (Achillea millefolium). These flowers are shallow, easily accessible to insects.

Blanketflower (Gaillardia aristata) is just starting to bloom, its striking heads like miniature sunflowers.

Prairie flax (Linum lewisii) has a few open flowers and many slender, nodding buds. Earlier this summer, I noticed several small and medium-sized bees visiting these blooms.

Here’s a patch of wild licorice (Glycyrrhiza lepidota). This native relative of cultivated licorice (Glycyrrhiza glabra) has bur-like brown seedpods. I’ll admit that some people don’t like this plant because of its burs. But bumblebees love the white flowers, which will open up in a few more weeks. And last summer, I found a patch where over 50 ladybugs were feasting on aphids. Do you have aphids in your garden? Maybe a patch of wild licorice would attract some ladybugs.

Attract more bees

Today I’m picking and choosing, finding the native flowers scattered here and there. As I wrote last week, a sea of non-native smooth brome (Bromus inermis) dominates the habitat along this stream. But what if our streamsides held an abundance of all these flowers?

There would be patches of two-groove milkvetch for leafcutter bees, aphids, and ladybugs. We could tolerate some leafy spurge for ichneumonid wasps and biocontrol beetles. Yarrow, scarlet globemallow, and sandbar willows would feed other pollinator species. We could plant hairy goldenaster and wild licorice for mid-summer flowers. Rabbitbrush and goldenrod would feed insects in the fall. With all of these flowering plants (and a few dozen others we could think of), how many species of pollinators could we support? Hundreds?

Eventually, this is what I hope my yard will look like. And when it does, I have a feeling I won’t be worrying about aphids getting out of hand. (I might go crazy trying to understand all of that insect diversity, though!)

Learning from the milkvetch

Two-groove milkvetch is an interesting plant. Popular with a variety of bees, strikingly beautiful in bloom, and capable of accumulating selenium to levels that are toxic to many organisms, it’s something of an enigma. But although questions remain, a close look at the milkvetch reveals some general patterns that we can take to heart here in the midst of Pollinator Week. Here are some takeaways:

• There’s a lot more going on in our plant communities than first meets the eye.
• For pollinator diversity, floral diversity is a good thing. Milkvetch will attract some species, leafy spurge others, and globemallow still others.

It might not surprise you to read that I’m pretty excited about our local plants and the pollinators they support. And as I imagine habitats brimming with native flowers and filled with bees, I’d love to hear from you! Have you tried to add some native plants to your yard or neighborhood? Are there native plants that seem especially important for pollinator diversity? Have you observed anything related to two-groove milkvetch and selenium? Let me know!

Until next time, let’s take a moment to thank our local plants for supporting all of our pollinators. Maybe we can make space to add a few more to our yards or our neighborhoods.

Further reading

Wilson, Joseph S. and Carril, Olivia M. (2016). The bees in your backyard. Princeton, NJ: Princeton University Press.

The post How to attract more bees: plant milkvetch appeared first on Wild With Nature.

June 16, 2022

I think I may be the only person in Helena with a fondness for leafy spurge (Euphorbia esula). Yes, I’m talking about that leafy spurge, the noxious weed that everyone hates. I started to like leafy spurge last summer, when I noticed that the flowers seemed to be extremely popular with a diversity of colorful pollinators, especially wasps. The colonies I was watching were small ones along a stream. This was an area otherwise dominated by non-native grasses – grasses which offered essentially nothing for pollinators. Leafy spurge was one of the few nectar sources available – and it was extremely popular with the insects.

So is this noxious weed always horrible, as everyone seems to think? Or is there more nuance to this story? Today I’m going back for another look.

On this morning at the cusp of summer, the landscape is bursting with life. The hills are green from the recent rains. The meadowlarks are singing and the cottonwood leaves are out. Birds are everywhere.

The first spurge patch I visit is tiny, a few clumps flowering among a thick floodplain stand of smooth brome (Bromus inermis). Smooth brome is one of several abundant, non-native grasses that dominate much of the Helena Valley. Competitive, turf-forming, and prone to crowding out natives, it seems to harbor very little biodiversity. However, it makes a good pasture grass. Perhaps that’s why the State of Montana doesn’t consider smooth brome a noxious weed. Leafy spurge, on the other hand, is listed as “noxious.” According to the Montana Natural Heritage Program, noxious weeds are plants that “have a destructive impact on Montana’s landscape.” They highlight displaced native plants and lost wildlife habitat as particular concerns. Yet ironically, in my experience in the Helena Valley, smooth brome appears to pose a much greater threat to native plants and habitats than leafy spurge does.

Sleepy morning

Early on this sunny morning, these leafy spurge clumps are relatively quiet. But already, dozens of ants are busy on the stems. I spot a sleek, black-and-orange wasp flying from flower to flower. I swing my insect net and it tumbles in. 

Wasps are so diverse that to identify them to species usually means collecting them and studying them under a microscope. Judicious collecting has a negligible impact on insect populations (unlike habitat loss and insecticides), but I still try to minimize it. Today I will be collecting some of these insects, though. Over the winter, when I have more time, I’ll be trying to identify these creatures to species. Species identification is the key that unlocks any studies scientists have already done with these species. All winter long, I’ll be learning more about the summer landscape, trying to understand what all of these insects are doing in the ecosystem.

I transfer this wasp from my net to a killing jar, where it dies quickly from ethyl acetate fumes. Now I can look at it up close with a magnifying lens.

The wasp is surprisingly delicate in my hands. The black head and thorax contrast with the orange abdomen and legs. The slender, flexible antennae are made up of over 30 segments. These super-segmented antennae are found in only a few wasp families. This plus the pattern of wing venation tells me that this is an ichneumonid wasp (family Ichneumonidae). The ichneumonids are unbelievably diverse. There are well over 5000 species in North America, and many more that scientists have not yet described.  

What good are wasps?

“Wasps,” you may be thinking: “aren’t those the annoying creatures that hover around picnics and sting children?” Those wasps, the social vespids (such as yellowjackets and paper wasps) are actually just the tiny minority that give this whole, colorful group a bad name. The reality is that 99% of wasps go about their lives without any interest in stinging us. Many of these wasps still can sting – but you have to be trying really hard to get one to sting you. And because they don’t visit our picnics, you probably won’t notice them unless you’re looking for them. 

What good are wasps? To start with, they’re colorful, extremely diverse, and have fascinating life histories. They’re important pollinators (this is even true of the species that like to sting us, such as yellowjackets). And the vast majority are specialized predators or parasitoids. These wasps spend their lives hunting down specific insects. Depending on the species of wasp, they may attack cutworms, weevils, grasshoppers, aphids, other wasps, or even spiders – in short, basically any invertebrate imaginable. Many of these wasps help regulate potentially “pesty” herbivorous insects. All of them play a critical role in the complex food webs that surround us.

Wasps for farm and garden

What about the ichneumonids? These wasps are all parasitoids: females of each species seek a specific type of host insect and lay their eggs on it. Sooner or later, as the ichneumonid larvae develop, they kill their host. Because of this, ichneumonid diversity isn’t just of interest to nature-lovers and biologists. It’s also important to gardeners, ranchers, and homeowners – to anyone who has ever experienced an outbreak of some herbivorous insect.

It’s relatively easy to tell that a wasp is an ichneumonid: just look for the many-segmented antennae plus the pattern of wing venation. But from that point, identification is next to impossible. That’s why I’m very lucky to have some help from Brandon Claridge, an ichneumonid researcher who is working on his Ph.D. at Utah State University. Brandon’s research focuses primarily on certain groups within this massive family, but he has offered to take a look at any of the ichneumonids I can collect here. While identification will still be difficult, he stands a much better chance of making sense of these wasps than I do. And ichneumonids are very under-studied, so it’s quite possible that we may even find a species new to science here!

The next wasp I find on the spurge flowers is also an ichneumonid, its entire body brick-orange except for a patch of lemon-yellow under the abdomen. While I’m photographing it, I notice another, apparently identical wasp foraging on the spurge. It’s always reassuring to see that I haven’t collected the only representative of a species. Hopefully there are many more of them around.

More insects & weird flowers

Now a honeybee is visiting the bizarre yellow flowers of the spurge, buzzing steadily as it flies from one to the next. And although this patch is quieter than what I’ve seen in the past, already another ichneumonid species has shown up. This one is long and slender, another variation on the theme of orange and black. It has a strikingly yellow face.

I stop to watch one of the ants on a spurge flower, head buried in it, manipulating the stigmas. I see ants practically everywhere, so it’s easy to take them for granted. They’re surprisingly diverse and complex creatures, though. And I know practically nothing about them. Today I collect this ant from the spurge, hoping to learn more about this species in the lab this winter.

Now I take a closer look at the flower structures of the spurge, which are truly weird. A pair of greenish-yellow bracts makes a cup around a set of glistening, crescent-shaped glands, a platform from which a set of stamens and a single female flower emerges. Shooting off to the sides like miniature fireworks are two greenish cups, each housing another female flower and more crescent-shaped glands. There’s a reason these glands are glistening: they offer up sugar-rich nectar while the female flowers are open, attracting all of these wasps and ants.

Biocontrol beetles

Now I move to a slightly larger patch of spurge. Right away, I find a leafy spurge stem-boring beetle! After I get a few photos, it moves to the far side of the spurge leaf, hiding from my camera. Unlike the ichneumonid wasps, these beetles are fairly recognizable to species in the field (the fact that they’re perching on leafy spurge helps a lot). Intentionally brought here from places in Eurasia where leafy spurge is native (after careful study to make sure that they wouldn’t become invasive), these beetles (Oberea erythrocephala) are specialized herbivores that feed on spurge stems and roots. This is one of a number of biocontrol insects that have been released in Montana. The hope is that these insects will reduce the competitive edge of their host plants, allowing non-native plants like leafy spurge to “play better with their neighbors.”

A diversity of visitors

I manage to get photos of a small, docile red wasp visiting the outer, female spurge flowers. When I try to catch it, though, it eludes me. Sometimes I’m glad when that happens. I don’t like to collect, so sometimes I’m relieved when the insect gets away. This wasp has many-segmented antennae, too. I don’t manage to get a look at the wing veins before it flies off. In any case, though, this is another parasitoid, either an ichneumonid or one of their close cousins, the braconids.

The morning is warming up, but the wind is still gentle. These small patches of spurge are starting to get active. Ants are everywhere. A crane fly is nectaring on the flowers, awkward on its long legs. In a narrow patch of spurge along the stream, there are even several species of stoneflies feeding on flower nectar! I spot a small, black and yellow wasp (I suspect a predatory species in the family Crabronidae), but it flies off before I can catch it.

The diversity that is present here is astounding. One of the most common visitors is a black wasp (or is it a cleptoparasitic bee?) with a red abdomen. There are at least 20 of these visiting the spurge flowers.

More ichneumonids for farm and garden

There are so many ichneumonids! I find one that is jet-black with red legs.

Another is black with scattered patches of cream.

There’s a black ichneumonid with orange legs.

One has a strikingly patterned abdomen, orange at the base followed by black and white stripes.

I find an orange ichneumonid with dark-banded wings.

There’s one whose abdomen is the deep red of a Bing cherry.

This diversity is much more than just a pleasing kaleidoscope. Each species has its own life history, and each targets a specific type of insect as its host. If we could even begin to understand the complex ways that these wasps influence the local food web, it would be mind-blowing.

Flies and more

Although these parasitoid wasps are the most conspicuous and varied insects visiting leafy spurge today, they aren’t alone. I catch an elongate, hairy fly that I don’t recognize: another story to learn about later.

Another fly has a flattened body. Its thorax is covered with velvety golden hairs. I suspect this is a soldier fly (family Stratiomyidae). Many species in this family are flower visitors; the larvae are detritivores, breaking down decaying plants.

The diversity is overwhelming. I catch a large, extremely wary fly with a polished, metallic-blue abdomen: probably a blow fly (family Calliphoridae).

A few small, extremely active black wasps with iridescent blue wings are visiting the spurge. I catch one. This wasp isn’t an ichneumonid: the antennae are much less segmented (just 12-13 apparent segments). It’s a spider wasp (family Pompilidae). These fascinating predators hunt spiders, which the wasp larvae feed on.

At this point, I’m sitting in the shade of a chokecherry. It’s taken me several hours to photograph all of these insects and record their information. Now it’s mid-afternoon, and it’s becoming one of the first hot days of the year. The sun is shining. The breeze has become blustery, but it’s not strong enough to discourage pollinators from flying.

More pollinators on the landscape?

Done cataloging that batch, I head back towards the leafy spurge patches. But I have trouble getting there, because on the way I have to walk past the two-groove milkvetch (Astragalus bisulcatus). The huge, bushy purple clumps of this native legume are in full flower. They’re busy with activity, as well: honeybees, two species of bumblebees, and a variety of other hairy bees are going from bloom to bloom. Today I’m trying to focus on the leafy spurge, but it would be very easy to get sidetracked watching insects on the milkvetch…

The insect community on these purple flowers is strikingly different from the group visiting the spurge just a few feet away. Instead of slender wasps, the prominent species here are fuzzy bees. And the striking difference in these communities suggests an intriguing idea: might patches of non-native flowers actually increase the overall numbers of pollinators present in an ecosystem?

This question hinges on whether plants like spurge are creating additional pollinator habitat, or whether they are just “stealing” pollinators that are already present from adjacent, native plants. In 2003, Vincent Tepedino and several other researchers took a look at this question in a park in Utah. Focusing on bees, they found that native plants on their study site attracted different, more specialized pollinators than did non-native plants. Based on this work, they suggested that, at least under these conditions, the presence of non-native species may boost a landscape’s carrying capacity for bees.

Bees here, wasps there

Today in this habitat, as in the Utah study, it appears that the non-native leafy spurge and the native two-groove milkvetch are supporting vastly different pollinator communities. It seems to be providing habitat for a variety of species that otherwise wouldn’t be here. So far I’ve seen only a very occasional bee on the spurge, while the milkvetch is hosting many bees. Meanwhile, spurge nectar is proving very attractive for ichneumonids and other wasps. I’m not seeing these species at all on the two-groove milkvetch.

Some more wasps and flies are visiting the leafy spurge now. I catch two tiny, iridescent cuckoo wasps (family Chrysididae). Like so many insects, these beautiful wasps have bizarre life histories. The females of most species are parasitoids on particular bees and wasps. They’ll sneak into the nest of a host and lay their eggs. If they are successful, the cuckoo wasp larvae will develop by feeding on the young of the host. Gruesome!

Then there’s a bee fly – a member of another group of parasitoids (family Bombyliidae). This one is small and fuzzy, with a dark stripe along the front of the wing.

Leafy spurge and insects

Where would all of these insects go if the leafy spurge were gone? Presumably most if not all of these pollinators are native species. (I’ll find out for sure when I identify them this winter.) If so, they were able to survive on this landscape before leafy spurge showed up.

But it’s different now than it was then. The area along this stream isn’t rich in native plants. It’s mostly covered with smooth brome and other competitive, non-native grasses. When people try to manage weeds, they usually ignore these grasses (as well as any nearby native plants). The grasses are as competitive as spurge, though, and much more abundant. And in the midst of this sea of grass, these small colonies of leafy spurge are providing habitat for a complicated, diverse, striking community of insects.

Beyond kneejerk reactions

Let me be clear: leafy spurge can be a serious threat to native plant communities in some areas. It occupies millions of acres across the west. I’m not trying to deny that leafy spurge can pose threats to native plants – and there are undoubtedly times when thoughtful management to reduce spurge populations will be appropriate. But far too often, invasive plant management is nothing more than a poorly informed, kneejerk reaction. When we label leafy spurge as “bad” – without even asking what it’s doing here – and then spare no expense to destroy it, I would argue that we, not it, are the invasive problem.

And in the case of today, we just have a few small patches of leafy spurge in heavily grass-invaded habitat, with biocontrol insects already present. Here, I believe that the only responsible management option is to leave it alone. Let’s enjoy this leafy spurge, with its weird flowers and all of the wasps that are benefiting from it. This “horrible” weed is helping our pollinators. And instead of trying to eradicate a few little patches of spurge, let’s dig up a patch of smooth brome. There, next to the spurge, let’s plant some milkvetch and other natives, and watch the pollinators hum.

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