Black-and-White “Dancing” Caterpillars

2013 April 17

On June 13, 2012, Sandy found this rolled-up goldenrod leaf with a little caterpillar inside.

When it came out, we saw it was a pretty little thing, with black-and-white stripes.

It finally dropped completely out of the leaf for photographs.

Checking the side, we can see that it has the right number of legs to be a caterpillar, not a sawfly.

But the most interesting thing was that, when touched, it would suddenly go into an explosive “dance”, and then dash off at a really fast clip (well, fast for a caterpillar, anyway). (The next picture is supposed to be an animated GIF[1]. If it isn’t moving for you, something is wrong).

Well, that’s amusing!

And then, about a month later on July 3, 2012, we found a similar caterpillar in the dog’s food bowl[2], of all places. And it did the same kind of dance-and-dash when touched:

It wasn’t identical, though. In addition to being bigger, it had yellow-orange splotches along its side and a single row of white spots down the back.

And instead of a black patch behind the head, it had a patch that was black with thin white stripes.

As distinctive as these are, I thought they’d be easier to ID than they turned out to be. I went through every book I had with no luck, and couldn’t hit the right search terms to find them in BugGuide. Finally, on BugGuide John and Jane Balaban pointed me to the Twirler Moths in the family Gelechiidae, and specifically to the genus Dichomeris for the smaller black-and-white one.

I assume that the larger black-white-and-yellow one is probably also a Twirler, but I still don’t know which one. It could be another Dichomeris, since there are 75 species in the genus and BugGuide only has pictures of four of them.

The weird thing is that I’ve been searching around for some time now, and nobody mentions the “dancing” behavior. Which I would think would be distinctive and unusual enough to be worth noting. Well, if nobody else is going to do it, I’m mentioning it!

[1] It turns out that the free ImageJ software that I use for photo editing is also perfectly capable of quite a a lot of video manipulating, including extracting individual frames, cropping, and converting short video clips into animated GIF files. You know, for a piece of freeware originally developed by a bunch of microscopists to serve their own specialized purposes, ImageJ is actually pretty darned capable. And in a case like this where I’m dealing with only a few seconds of relevant video anyway, I think an animated GIF is more appropriate than mucking around with YouTube.

[2] In the summer, we sometimes fed the dog outside. So no, the caterpillar didn’t get into the house. This time.

One Response
  1. April 17, 2013

    Cute little guys!

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