April 27, 2023
If you hate spiders, I have bad news for you: the world is full of them. In the state of Washington alone, there are at least 970 species. But in spite of many peoples’ prejudices, this is actually good news! Of the 970 spiders in Washington, only one species, the western black widow, can be somewhat dangerous to humans. And our incredibly diverse spiders—many of them the size of a pinhead and ignored by almost everyone—play an important role in terrestrial food chains, eating literally tons of insects as well as feeding salamanders and birds.
Rod Crawford is no stranger to pinhead-sized spiders. For the past 52 years, he has been studying Washington’s diverse spider fauna. Rod is the curator of arachnids at the University of Washington’s Burke Museum. His research involves collecting spiders from different habitats all across the state, identifying them, and maintaining the Burke Museum’s impressive arachnid collection. (Read more about Rod, and find accounts of his frequent spider-collecting forays, on his website here.)
Today Rod and I are parked alongside a gravel road in a patchwork of forest and clearcuts near Oakville, Washington, about 30 miles southwest of Olympia. We’ll be spending the day collecting spiders here: part of Rod’s ongoing effort to fill the gaps in our knowledge of the state’s spiders.
Spiders and their habitats
Spiders are generalist predators, eating just about any insect or other small creature that they can chase down or trap in their webs. How, then, do 970 species manage to live in Washington without all competing for the same foods? Spiders, it turns out, specialize in the microhabitats where they live and in how they hunt.
Certain spiders only live on sagebrush. Others find shelter among the evergreen needles of conifers. Still others, incredibly, are found primarily in fallen pine cones. And of course, some species are generalists, occupying a broader range of habitats.
Hunting strategies vary, too. Many species weave webs, which range in appearance from sheets to funnels to orbs. Others, like the wolf spiders (family Lycosidae), chase their prey across the ground, moving rapidly on their eight legs.
The patchwork of forest and logging roads that we’re searching today has five major microhabitats we can check for spiders.
“The major habitats here are going to be sifting litter, sifting moss from trees, beating the sword fern understory, sweeping grass and roadside herbs, and beating conifer foliage,” Rod tells me.
There are a few other places we can also look if we have extra time. The wolf spiders, those web-less hunters, run across the ground in open areas. There are certain spiders that hide on downed wood in the forest. Meanwhile, other species are associated with wetland areas.
Spiders of the deciduous leaf layer
I follow Rod as he begins checking the first habitat, the deciduous leaf litter. We climb down a slope where mature red alders (Alnus rubra) cast their shade on a low layer of redwood sorrel (Oxalis oregana) and Pacific bleeding heart (Dicentra formosa). Beneath the spring herbs, the blanket of last year’s dead leaves smells of rich earth. We focus on patches where the red alder leaves (Alnus rubra) have piled up deep under the sword ferns (Polystichum munitum). Rod takes handfuls of the moist leaves and shoves them into a black plastic trash bag.
When the trash bag is full of leaves, we return to the hood of my car, where Rod has spread out a piece of canvas. He scoops clumps of leaves into a tub with a coarse-screened bottom, letting small creatures fall through onto the canvas. Now we begin the laborious process of picking out tiny spiders, which Rod will collect for the museum.
It’s one thing to know, intellectually, that there are lots of tiny creatures living in the leaf litter. It’s another thing entirely to actually see this complex community, this diversity of common but seldom-seen creatures. There are springtails, mites, rove beetles, centipedes, carabid beetles, isopods, millipedes, and more. From time to time we see pseudoscorpions, which look like tiny lobsters with dark red pincers.
Life among dead leaves
Rod is a taxonomist of the leaf litter, rapidly outpacing my grasp of scientific Latin as he rattles off the names of the creatures he’s seeing. To identify most of the spiders to the species level, he’ll need to look at them under a microscope in the lab, but he is able to recognize many of them to the genus level in the field. And he can identify much more than just spiders, naming particular isopods, centipedes, and millipedes as we run across them.
Once we finish with the alder leaves, we take a sample from beneath a bigleaf maple (Acer macrophyllum). Rod pulls out a clump of whitish fungal threads from among the leaves.
“Collembola food,” he says, referring to the springtails by their scientific name. These creatures are decomposers, feeding on fungi and fallen leaves. The food web of this world in miniature—fueled by a fresh pulse of deciduous leaves every fall—is becoming apparent.
It becomes even more apparent when we find a red-backed salamander (Plethodon vehiculum) among the damp maple leaves. These lungless salamanders breathe through their skin and live in moist areas, where they hunt spiders and other small invertebrates. This one isn’t much more than an inch long. We quickly return it to the moist leaf litter below the maple.
Later, we find a second red-backed salamander, this one as long as my middle finger. It’s a sign that this is a high-quality forest floor, Rod says.
The spider diversity reflects the quality of the habitat here, too. “This has been a pretty good litter sample, probably eight or ten species [of spiders],” Rod continues.
Spiders of the mosses
Now it’s time to search for arachnids among the mosses. Thick, moist carpets of moss on the trunks of deciduous trees make excellent homes for certain spiders, Rod tells me. We set forth into the forest again, collecting samples of moss to screen for invertebrates.
The moss is mostly dry after several days of sunny spring weather, and it’s dusty from the nearby logging road. The invertebrates we’re finding here seem rather less abundant today than in the leaf litter—mostly isopods, rove beetles, and jumping bristletails. But, as Rod predicted, we also find some different species of spiders. Rod shows me the yellow-tinged Ethobuella tuonops. This is one of the most common spiders in Washington’s mosses, he tells me, but it’s rarely seen because so few people do this kind of careful spider search.
After hours of sifting through leaves and moss, it’s time for a change of pace. Rod sends me to collect spiders from roadside grasses and herbs while he collects from sword ferns in the forest. After the painstaking sifting, sweeping an insect net through the grasses, coltsfoot, and wild carrot is a refreshing change of pace. It’s easy work, but it gets exciting when I stop and open up the canvas net to see what I’ve caught.
The spiders of the roadside herbs and Douglas-firs
The community is very different here. There are beetles and bugs of many shapes and sizes, along with the occasional wasp. And then there are the spiders. Even to my novice eye, it seems there must be at least eight species here. There are reddish spiders and black and white spiders; leggy spiders and compact spiders; jumping spiders, crab spiders, and many others I don’t recognize. I scoop them up into a vial for Rod to identify later.
The afternoon is nearing its end now. Soon it will be time to pack up and get on the road. But first we need to check the Douglas-fir needles. Conifer foliage, it turns out, can be a very productive habitat for spiders. It makes sense: while the alders and bigleaf maples shed their leaves every fall, feeding the springtails, spiders, and salamanders of the forest-floor community, the firs hold their needles year-round. The living fir foliage forms a microhabitat that’s stable enough to provide homes for a variety of species.
The Douglas-fir branches give off a pleasantly spicy, resinous scent as I beat them over my net. Here the spiders—an abundant assortment, most of them pinhead-sized—are accompanied by weevils, ants, and brownish inchworms. I’m continually surprised by their intricacies—and grateful that my macro lens allows me to see the details. These spiders, some of them only as wide as a fir needle, are beautiful, with fine patterns in charcoal, yellow, and white. One has a broad-striped abdomen and long reddish legs. Another is a pleasing orange, marked with a narrow triangle of white hairs.
Getting to know an unseen community
By the end of the day, we’ve collected 46 species of spiders within an area the size of two football fields. It’s a diversity that is mind-boggling to a novice like me. Each species has its own story: where it lives, how it hunts, how it interacts with the community around it. And besides the spiders, we’ve gotten to know some springtails, red-backed salamanders, ground beetles, and inchworms. In this small patch of western Washington forest, we’ve seen hundreds of species. We’ve witnessed how microhabitats support a wonderful diversity of animals. From moist maple leaves to mosses, from roadside grasses to Douglas-fir boughs, the forest is making homes for an abundance of life.
As we get ready to leave, I can hear the liquid trill of a Pacific wren in the distance, spilling out his song in an energetic cascade. It’s a soothing sound, one I’ve heard many times before—but now it means something new to me. Like red-backed salamanders, Pacific wrens eat spiders. As I see this forest through fresh eyes, noticing all of the ways it provides homes for spiders, I’m able to hear the song of the wren as an ode to this diversity. As long as bigleaf maples shed their leaves and mosses grow on their trunks, he seems to be saying, there will be spiders here—and so will I.
Many thanks to Rod Crawford for not only taking time to teach me about spiders, but also for identifying the spider photos featured in this article.
Crawford, R.L. (2023). Spider collector’s journal: narratives of spider collecting trips. Retrieved from https://crawford.tardigrade.net/journal/index.html
Ramseyer, L.J. & Crawford, R.L. (2014). A survey of spiders found in fallen pine cones in eastern Washington State. Western North American Naturalist 74(4):405-415. Retrieved from https://bioone.org/journals/Western-North-American-Naturalist/volume-74/issue-4/064.074.0406/A-Survey-of-Spiders-Found-in-Fallen-Pine-Cones-in/10.3398/064.074.0406.short
Towes, D.P.L. & Irwin, D.E. (2020). Pacific wren (Troglodytes pacificus), version 1.0. In Birds of the World (A.F. Poole, editor). Cornell Lab of Ornithology, Ithaca, NY. Retrieved from https://birdsoftheworld.org/bow/species/pacwre1/cur/introduction