The BugLady loves crab spiders, so she’s been thrilled to find two, new (to her) species in the last few years. One, the Whitebanded crab spider, is in the family Thomisidae, a family of, well, crab-shaped spiders, many of whom make their living on flower tops, and many of whom, in the genera Misumena, Misumenoides, and Misumenops (Mecaphesa), can be tricky to ID. We’ll meet the other one next week. 

Whitebanded crab spiders (Misumenoides formosipes) (formosipes is from the Latin for “beautiful leg/foot”) are named for a white band that crosses their face, right below the level of the eyes (depending, of course, on whether the spider is right-side-up or up-side-down). But there’s a catch. Like the very common Goldenrod crab spider (Misumena viata), female WBCSs can change colors depending on where they’re sitting – from white to yellow and back – by secreting or excreting yellow pigment from their normally-white outer cell layer (cuticle). Turning yellow takes longer – up to three weeks – than does reverting to white. In its yellow form, it could be called the Yellow-banded crab spider . Other common names include Red banded crab spider and Ridge-faced flower spider.

They’re widespread, found in Ontario and much of the US, excepting the Northwest quadrant. 

WBCSs have eight eyes – four are arranged in a straight line, two are above that, and the other two are around the edges. As is common in spiders, females are much larger than males, and they have dark markings on their legs, which separates them from some of the other genera of flower crab spiders. Females come in a variety of colors , , and . Males typically have a red/orange/gold abdomen, and their four front legs are dark , but they can’t switch colors.

WBCSs don’t make trap webs; they’re ambush predators that hang out on flowers and attempt to grab any visitor to the flower that looks toothsome, even if it’s slightly larger than they are. They are frequently collected by various mud dauber wasps – stung, paralyzed, and used to provision the wasp’s egg chambers – food for eventual wasp larvae. Spider eggs and spiderlings provide food for lots of predators. 

Males, especially when they are actively hunting for a mate, are nectivores, feeding on pollen and nectar, especially on Queen Anne’s lace. Searching for a mate takes up a good deal of a male’s time, so he employs a “Bird in the Hand” strategy. He locates a female before she becomes fully mature (unmated penultimate female), and he guards her until she is old enough to reproduce. He lives on her inflorescence and takes on rival males, but despite his devotion – and energy investment – whichever male is closest after she undergoes her final molt will likely be the lucky spider, although the resident male does have the home-field advantage. 

Female WBCSs like Black-eyed Susans, and males search for likely flowers by their smells. His small size and light weight allow him to jump from one flower head to another or to loose a line of web into the wind and to tightrope across it after it sticks to the next flower.

Females create silk sacs holding 80 to 180 eggs, attach them to leaves, and guard them until she eventually freezes. The spiderlings exit the egg sac in spring. 

Yes – they do eat pollinators, and everyone loves pollinators. But these are native spiders feeding on native pollinators, and they worked all that out a long time ago – their food habits don’t upset the Balance of Nature, and they supply protein for larger critters. Some apologists point to the fact that the presence of predators improves the defenses of prey species over time. 

Go outside, look for bugs! The BugLady visited a wetland on a warm day recently and saw some Common Green Darners messing around in a stand of last year’s cattails.

The BugLady

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