Zebra Jumping Spider with Caterpillar
Back on May 31, 2020, Sandy spotted this example of a jumping spider subduing its prey.
The spider is a female Zebra Jumping Spider, Salticus scenicus, a very common and extremely distinctive little spider. I’m not sure what the caterpillar was, other than that it was probably immature, and it was fighting pretty vigorously. The spider had it by the head, putting it at kind of a disadvantage.
The caterpillar probably outweighed the spider considerably, and they were tussling all over the place like a couple of wrestlers.
The spider has two huge advantages in a situation like this:
One is that she is injecting venom the whole time. Since she has hold of the head, it is going straight into what passes for the caterpillar’s brain, for maximum effectiveness. All she really needs to do is avoid losing track of the caterpillar until the venom takes effect.
The other is that the caterpillar just has stumpy little legs and all it can really do is thrash about. In contrast, the spider has eight fairly agile legs that she can use to largely control where the combat goes. It was still pretty hard sledding for her, though. The caterpillar was throwing her all over the brick they were sitting on. They largely ignored me as I was taking pictures, but as you can see they didn’t exactly stay still to pose for me (nor did I expect them to).
This is probably about as big of a prey item as a jumping spider can reasonably manage. Any larger, and it would have been able to throw her off and probably escape. This is in contrast to a web-building spider, who can use their webbing for most of the prey immobilization. Web building spiders can routinely catch prey up to ten times their size because of that.
The downside of the web approach, though, is that a web has to wait for something to blunder into it. And things like this caterpillar don’t normally blunder into static webs. This is why the jumping spiders can make a go of it as active hunters: they can spot, stalk, and attack prey that is not cooperatively stumbling into a web, and so they have a better selection. So even though the jumping spider can’t manage really big prey, they can catch a greater number in a given amount of time, and it all evens out.
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Wonderful photos and essay.
One nuance to the web-advantage is the home-turf advantage. A spiders’ legs will grip tenatiously and travel very quickly on its own web. Most prey simply can’t push hard enough out of the webbing. Most webs also have a retreat, in case the prey turns out to be too dangerous. A nomadic jumping spider doesn’t have such advantages, which makes their prey catching ability all the more impressive to me.