Brown Densely-Furred Caterpillar

2012 March 21

We found this caterpillar on a tag-alder leaf on September 1, 2011. It was a bit cold that day, and the caterpillar was practically comatose. Until we carried it into the house, that is. Then it rapidly warmed up, and suddenly became very active. The whole time I was trying to photograph it, it ran and ran and ran and ran. It was pretty fast for a caterpillar.

I’m pretty sure that it had a long tuft of black hair on its rear when we caught it, but this tuft then went missing before I could get the pictures. It also looks as if it may have lost a lot of hairs from its head end, probably in some sort of rough-and-tumble with a predator that ultimately decided it wasn’t going to be so good to eat after all.

Anyway, it has a black head, and little pink prolegs

And its skin under all the bristles looks to be black.

Hairy caterpillars like this that one finds in the fall generally turn out to be some kind of Tiger Moth, tribe Arctiini, so that’s where I went looking for a match. I’m not finding anything that’s a clear match as this one stands, but if we look at the Banded Tiger Moth, Halysidota tessellaris, everything looks pretty close except for one thing – the long, black tufts of hair at the head and rump ends. Delete those, and it’s a pretty good match, with the same dense, brown uniform-length hairs, slightly hunchbacked appearance, and slightly darker stripe running down the back

If (A) those long black tufts are defensive hairs that easily come loose when the caterpillar is attacked by a predator, and (B) this caterpillar did in fact survive an attack before we found it, then the Banded Tiger Moth is a pretty good candidate. If they don’t then it must be something else. Still, we found it on a tag alder bush, and alder is listed as a Banded Tiger Moth foodplant, so overall it’s looking more likely all the time.

6 Responses
  1. March 22, 2012

    Amazing deduction, Holmes! You astound me!


    I wonder if you could use these guys like pipecleaners…

  2. March 23, 2012

    Self-actuating pipecleaners! Set them at one end of the pipe, put some attractant at the other end, and let ’em rip!

  3. March 23, 2012

    What you need to invent is a micro fan that blows air across a tiny piece of cloth moistened with the scent of crushed alder leaves.

  4. March 28, 2012

    This post sounds like a cut out from a Dr. Seuss book–and he ran and ran and ran…..until he turned into a butterfly.

    This caterpillar looks like twist ties of wool.
    I can’t believe he is balding–he looks like a small rug.
    He has a remarkably handsome face–the side profile view is almost classically charming.

    You obviously don’t have entomophobia since you have this bug in close contact with skin surfaces.

    Just looking at its fuzziness makes me feel slightly ill and I can’t imagine it on my finger.

  5. Teresa Bobel permalink
    September 9, 2018

    we found the exact caterpillar! my little girls were very excited! what does it eat though?

  6. September 10, 2018


    They eat the leaves of lots of different types of trees. The ones listed on BugGuide are
    alder, ash, birch, elm, hazel, hickory, oak, poplar, tulip tree, walnut, and willow.

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