It’s not often that you hear the words exquisite, pink, and camouflage come together in a sentence. It’s even rarer when “spider” is added to the narrative.
But that’s exactly what happened during a recent walk at Fermilab when our group, gathered to learn about local bees, encountered a member of Thomisidae, the crab spiders.
The day was warm but breezy, which made hunting for our target species a little tricky. They were out there, for sure, but the gentle winds kept them from flying as freely as I’m sure they would have preferred. (Bonus: The breeze also kept mosquitos at bay.)
What was not ideal for Hymenopterans and Dipterans, however, proved to be near perfect for spiders in general, and crab spiders specifically. With flight somewhat difficult, a lot of the winged insects were staying low, near the plants. And while the plants held what the flyers were looking for—namely pollen and nectar—they also held spiders.
Lots of spiders spin webs in order to capture prey, and these structures—active as well as abandoned—were visible between the stems of many plants. They held the remnants of meals past, and stood as a great testament to just how many spiders a prairie can support.
I was just starting to think about how spider species progress through the summer, from tiny ones in early spring to large ones in late summer and early fall, when someone in our group spotted the first crab.
She was so well camouflaged, it was hard to pick her out at first. She was ensconced in the broad flower of a cow parsnip, and the pink zig-zag pattern on her abdomen matched the irregular edges of the petals almost exactly.
Boy, did she look crabby—in a good way. These spiders are named for the way their first two pairs of legs are elongated and reaching forward, much like that of a tasty sea crustacean. (Fun fact: If the second pair of legs is longer than the first, the crab spider is a running crab, family Philodromidae. These guys don’t hang out on flowers but are occasionally found in houses and are sometimes mistaken for brown recluse spiders.)
True to her type, this spider’s front legs extended out a long ways from her body. Strong claws at the end of these legs are ideally adapted to their main function, which is grabbing prey. Rather than spinning a web, crab spiders lie in wait and ambush unsuspecting insects.
When disturbed, crab spiders share another trait with their ocean-dwelling namesakes: They scuttle sideways.
That’s exactly what “our” spider did. As we, one by one, visited the flower on which she perched, her posture changed ever so slightly from offensive to defensive. Crab spiders, though predators, also are prey for a number of other animals, including wasps, birds and other spiders. As we moved one way and then another to ooh, aah and take pictures, Ms. Spider decided she’d had enough. In a sideward flash, she was gone.
Thanks to the Fermilab prairie’s bountiful diversity, though, we didn’t have to look far to find another parsnip umbel, and another crab spider. She was nearly identical to the first, and I wish I could say exactly what species they were. But proper identification requires a good look at eye arrangement as well as familiarity with the crab spider species in our area. And I had neither.
So for now anyway I won’t know whether the individuals we saw that day are one of the types that can change color to match their background—an amazing feat no matter what, but especially for a creature encased in an exoskeleton. I also don’t know for sure whether the males of this species consume nectar, which is another cool crab spider behavior arachnologists have discovered.
But you know what? It’s all good. Our time on the prairie that day was glorious. And the chance to see a pink spider, exquisitely camouflaged, is reward in itself.
Pam Otto is the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-513-4346 or potto@stcparks.org.