Storytime 2

cribellate orb weaver, possibly Uloborus glomosus, at buffet
This is a spider from the family of cribellate orb weavers – near as I can tell, this is a genus Uloborus, and from the active range I’m leaning towards a U. glomosus. Curious body structure, to be certain, but this image from August 2010 marked the first time (and so far, the most detailed) that I captured a specimen from this family. They’re distinctive in that they’re the only spider family that has no venom.

Now, the first thing I have to point out is that the reddish-brown thing is not its head, but its current meal, or what’s left of it – the arachnid was apparently loathe to relinquish the morsel even while it trussed up a brand spanking new leafhopper. Which is faintly amusing to me, because most monkey species will drop whatever food is in their hand if they have the opportunity to grab some more. This misshapen meal was blocking the spider’s eyes, so you’d think that was reason enough to at the very least set it aside, perhaps anchored someplace if the spider could determine some method of doing this, while putting its new meal in the to-go box, but here we are.

Curiously, from the series of photos that I got at this time, it would appear that the species actually has fangs (chelicerae,) and so we come to the part that I’m wondering about, because as I said, they have no venom so they need nothing to administer this lack. Perhaps they have the fangs just as a prank, like those little spring-loaded fake stage knives, so they can scare their prey species:Ha ha!” they say right after they have plunged their fangs into a cringing caterpillar, “You thought you were going to start dissolving from the inside! That’s two for flinching!”

This is the hazard of getting information in little chunklets, often from unreliable sources, because I’ve been slowly revising my understanding of arthropod habits over the years and (patently) don’t have an adequate understanding of them yet. Having been told that spider venom liquefies the organs of their prey so they spider can simply suck out this milkshake, I assumed that these handy little piercing bits also worked as straws. But no, the chelicerae are only venom-injectors; not all that long ago, I learned that spiders actually have mouths, hiding underneath behind the chelicerae, and that some of them simply chew up their prey (or what passes for such with their anatomy, anyway.) So, why does this species have them fangs? And two things occur to me: 1) because this family evolved from another which did have venom, and have the leftover fangs; or 2) that the chelicerae are functional holding/manipulating digits in their own right, which this photo would seem to attest to. Though I suppose there’s always a third option, which is that they obtained the fangs with the intention of developing venom, but just never got around to it. I know where I’d be putting my money…

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