Insect Picture of the Day

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Meet steatoda triangulosa, my favorite of all spiders. The name means “triangly combfoot”. If you could see her back, you’d see the telltale pattern of triangular chevrons that gives her species its name. The combfoot is her family of spiders and refers to a fine array of hairs on her feet that enable her to walk along her cobwebs with ease. This little lady is our bathroom concierge; I mentioned her in an earlier post. Here she is, behind the door, doing her job of keeping our bathroom area free of this tiny darkling beetle. She’s only about 5mm long (eyes to spinnerets, remember–legs don’t count) but don’t let her lack of size fool you. She works as hard as any spider twice her size. I say that steatoda is my favorite spider, which is funny because I like to play with jumping spiders more, and I think orb weavers are more photogenic. But steatoda is the one spider I let run freely through my home. I have kept some spiders as pets, but steatoda is allowed to live with me.

Here’s why: You are looking, my friends, at the absolute number one natural predator of hobo spiders right there. They are death on house spiders of all sorts. You get a colony of steatodae going in your home, and you can pretty much write off giant house spiders, barn funnel spiders, and hobo spiders. What do those spiders all have in common? They wander your home at night, they hunt by touch rather than sight, they’re aggressive, and they are all completely unable to cope with the combfoot tangle web. This little spider is a considerate housemate: she builds her cobwebs in out of the way places, doesn’t wander into beds or shoes or clothing at night, and she’ll eat anything that gets caught in her web–even things ten times her size. Oh, and she occupies the same ecological niche as black widows, so she puts competition pressure on them, too.

A few months ago, Liz got a nasty spider bite in bed. The weather had turned hot and some of the yard spiders had decided to share our air-conditioned bedroom with us. We spotted the spider most likely responsible but it eluded capture. Two days later he turned up–in the web of this very spider. He was three or four times the size of our concierge, but it didn’t matter–he was folded up in a wad of silk and being cheerfully devoured by our little combfoot.

I have noted in the past that jumping spiders don’t often eat insects with hard shells like beetles or even ants; as you can see from this picture a hard shell is not a viable defense against steatoda triangulosa. What she is doing, by the way, is gift-wrapping the beetle for later. She’s in “gantry mode”, hanging entirely from her second pair of legs (the ones raised up high). The other three pairs of legs work in concert, and they each have a function. The front pair of legs turns the beetle over and over, rolling it in the silk. The third pair of legs holds the beetle steady at each end for turning, like you and I would hold corn on the cob. The fourth pair of legs is the busiest, doing a sort of reverse bicycling motion: what they are doing is picking up strands of silk from her spinnerets and then slapping the silk against the beetle as it is turned.

I just went downstairs to check on her “boneyard”, the area of floor underneath her web (cleaning it up would require destroying her cobweb), and in addition to the previously mentioned spider, there are corpses of dozens of gnats and mosquitoes, half a dozen darkling beetles like this one, a dead cricket easily five times her size, and an earwig.

An earwig! THAT, my friends, is why steatoda triangulosa is my favorite spider.