Hydriomena Moth

2012 June 9

This is an early-flying (May 16, 2010) moth that came to our porch light, but this time instead of being on the siding, it was up under the eaves.

Following the suggestion of Steve Nanz on BugGuide, it looks a lot like the members of the genus Hydriomena. These are geometrid moths, with inch-worm caterpillars, and unfortunately there are 56 species in North America which all look a lot alike.

My specimen has a rather long snout, which as far as I can tell the Hydriomena don’t generally have (although some do). But I’m not seeing any “snout moths” that look like all that likely of possibilities either, so we’ll stick with Hydriomena for now.

A lot of moths have this fringing of hairs on the trailing edge of their wings, so it must serve some purpose. It would be interesting to do an aerodynamic study of moth wings to see if that fringing changes their flight characteristics at all. I suspect that they muffle sound – it might be what is responsible for the quiet, “mothy” sound of a moth flying, compared to the harsher flapping or buzzing sound of most other similar-size insects.

So anyway, assuming that this is a Hydriomena, a lot of them are northern species that eat the sorts of trees that grow in cold climates (mostly conifers like spruce and pine, and hardy shrubs like alder, hawthorn, and willow).

4 Responses
  1. June 9, 2012

    Is the powder that comes off when you touch a moth just sloughed-off skin cells?

  2. June 9, 2012

    We have a lot of these around south-west Michigan. I grew up finding them all over the place. This particular look has always been special to me, because as a child, I remember someone showing me these, and describing protective coloration and thus the basics of evolution.

  3. June 9, 2012

    Their wings form such pretty curtain fringes. They must camouflage well with the plush weave and pattern they exhibit. I’ve never seen a moth up close and that “snout” (is that an etymologically apt term?) seems rather adverse. I like your idea of the curtain fringe on the wings muffling their moth sounds near the back porch lights. I never hear them coming until they are before me and this would explain their irreversible silence.

  4. June 10, 2012

    KT: The powder is tiny colored scales that covers the wings of butterflies and moths. These scales are the source of their colors and patterns. If they are wiped off, then the wings are transparent. The scales are basically color pixels. There are links to a lot of micrographs of butterfly and moth wings here, if you’d like to see this in more detail:


    Andy: It seems like moths always get used as great examples of evolution, probably because they are (a) successful, (b) diverse, and (c) have come up with about a thousand distinctly different ways to mimic tree lichen and bird droppings.

    Julie: One other thing I didn’t mention about the fringes, is that for a lot of moths they also help the wings blend in with the surface they are sitting on. When the edge of the wing is pressed against, say, a lichen-covered tree trunk, the fringe breaks up the outline so the seam between wing and bark is hard to see.

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