Early Button Slug Moth

2016 November 2

This small brown moth (a bit bigger than my fingernail) came to our porch light on June 25, 2016.


The way that it holds its abdomen tip curled to point straight up makes me think that it was spreading scent to attract a mate, which in turn suggests that it is a female[1].


It eventually moved around enough that I could see the eye, at least, but the head was mostly obscured and the antennae were tucked neatly away.


It turns out that the pose is pretty diagnostic, I found what looks like an exact match on BugGuide pretty quickly. I think it is an Early Button Slug (also known as a Warm-Chevroned Moth), Tortricidia testacea.

This is my first specimen of one of the Slug Moths, family Limacodidae. For some reason, I had thought that this was a mostly warm-weather family[2] and that they weren’t found this far north, but here it is. Moths in this family have kind of blobby caterpillars with the legs not visible, that seem to stick to surfaces kind of like slugs. This particular species has a caterpillar that is a hairless green ovoid with a kind of reddish-tan bullseye in the middle of its back, and eats things like birch, black cherry, oak, and similar broadleaf trees. Other caterpillars in this family may have stinging hairs that makes them unpleasant or even actively dangerous to handle, although this species doesn’t look like it has any obvious defenses (and actually looks like it might be disguised as a bud).

[1] Although, it could also be calling a mate at ultrasound frequencies. The pose for scent distribution and ultrasound calling is similar, and unless I were to check within a few inches using a microphone sensitive to ultrasound above about 38 kilohertz, I’d never be able to tell. For reference, the upper limit of human hearing is only about 20 kilohertz, so this is well beyond what humans can hear.

[2] I probably got this idea from the fact that the better-known members of this family (like the hag moth, saddleback caterpillar, and the closely-related flannel moths), most definitely *are* warmer-climate species.

3 Responses
  1. November 3, 2016

    Off topic: Dude, did you see this?

  2. November 4, 2016

    KT: Boy. That’s quite a spider! I’m just sad that when I was in Australia, I didn’t find one of these.

  3. November 4, 2016

    I thought the thing poking out from underneath the wings was a radome.

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