Little Brown Inchworm with Black Splotches

2013 September 18

This little inchworm was caught by sweep-netting in the tall grass on August 23, 2012. It was busy trying to avoid notice by pretending to be a stick.

Sometimes, for variety, it would pretend to be a crooked stick. In this next picture, you can also see a small red mite near the bottom. The mite was barely visible to the naked eye, at about a millimeter.

Here’s a closeup of the caterpillar’s head, just in case there’s some diagnostic feature that someone recognizes.

And in this last picture, a queen ant (just barely visible in the bottom corner of the picture) brushed against the caterpillar’s feet, which scared it into tucking in its head and going into “full stick” mode.

The appearance isn’t very distinctive, and I didn’t find any really good matches in “Caterpillars of Eastern North America” (although there were a bunch that were vaguely plausible, and that had the note that they were “highly variable in coloration”). The fact that the caterpillar is so small (it was only about an inch long, and pretty thin) suggests that it may very well have been immature, which adds to the difficulty.

The only thing I really have to go on is that most of the twig-mimic inchworms live in trees, where mimicking a twig is good camouflage. And I found this one in the grass. Which either means that it fell off of a tree and got lost, or it normally eats grasses and/or forbs (flowering plants that are not trees, shrubs, or grasses).

There are still multiple possibilities among the grass/forb-eating inchworms, but the two most likely look to be either the Chickweed Geometer, Haematopis grataria (which has the closest match for coloration), or the Common Pug, Eupithecia miserulata.

I’d like to imagine that it’s the Chickweed Geometer, which is a beautiful yellow moth with pink stripes. But realistically, I think that the Common Pug is way more likely, since (a) they eat darned near anything; (b) their caterpillars are commonly found in the late summer/early fall, like this one was, and (c) I’ve already found one of the adults around here. And also, the Common Pug caterpillar is one of the ones that gets the “exceptionally variable” label.

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