Sunday, September 17, 2006
Bill and I were walking back up the driveway, having dropped the kids off at the bus, when we were arrested by this fabulous orange dye in a puddle. At times like this all my neurons fire at once. What made that stain? How come it's orange? Gotta know, gotta know...
So I bent down and discerned a lovely barrel-shaped caterpillar dropping at the origin of each stain. Imagine that much dye, packed into one pellet. We looked up and found a sassafras tree, well-chewed. Brain: clackety clack. Remembered that we used to boil sassy roots and got a very similar stain in the "root beer" we created. Must be a tannin of some sort. So the caterpillars are taking this in and dumping it back out as they chew the leaves. So much for tannins as chemical protectants. At least some caterpillars get around it by pooping them out. What caterpillars? Well, spicebush swallowtail is a real good guess. They're big, and abundant here, and they're all over the butterfly weed.
So get this: When a spicebush swallowtail is in its first three instars, it roams around on leaves. And it's black and white, and it looks exactly like a bird dropping! Who would eat that?Here, it's mad enough to have its osmetrium extended, and is probably exuding something noxious from those little orange "horns" over its head. (the true head and two front legs are visible beneath the osmetrium).
Younger instars are really dark and look even more fecal than this. Unfortunately, Internet piracy netted me no images. I owe these to the Net...wish they were mine.
Before it pupates, the later instar of this caterpillar rolls itself in a leaf, and binds the edges together with silk. In this instar, it has a fabbo snake face on its anterior segments. It stays in the shelter during the day (which is probably why I couldn't find the poopers), its head up. Should a worm-eating warbler probe into one of the rolled leaves, it would pop its scary "face" out of the shelter and scare the bejabbers out of the bird with its realistic "eyes." As an artist, the thing that flips me most about this kind of mimicry is the HIGHLIGHT in the fake snake eye! Check it out. There's a big white highlight on the yellow "lid," and a really cool smaller white highlight on the shiny black "eye." Please.
So how do you get something that perfect out of natural selection? Lots of folks would say God had to make that caterpillar, because it's too wonderful to have been arrived at through natural selection. I dunno. I'm comfortable with the concept that the ones that didn't look as much like real snakes got eaten by worm-eating warblers. Lotta years, lotta caterpillars, lotta warblers: snake eyes, moving toward perfection.
Humans as a species are so impatient. We can't fathom the pace and process of evolution. We want somebody to have made it with a snap of his divine fingers, or a wave of his wand. Somehow, that sort of mystical explanation makes more sense to many of us. We can sit back and accept that some entity rolled those tiny vessels and intestines and nerves, what, from some kind of caterpillar putty? Then baked it until it was done? It makes no sense to me at all. I think about it a lot, but the notion of divine creation rattles around in my head, and then falls out of my ear, plop! --spreading a stain in a puddle in the driveway.
For M. Rosetta Weiss
Posted by Julie Zickefoose at 3:14 PM