Isabella Moth

2012 May 23

The Banded Woolly Bear is one of the most well-known caterpillars in North America (and here’s a photo of one of them that I ran a few years back)

But, what does it turn into? [1] We decided to find out first-hand this past spring, so Sam caught a couple of banded woolly bears that had come out of hibernation during a warm spell in March 2012. We put them in a jar with some grass, and within about a week they both spun cocoons.

The first one emerged from its cocoon on April 9, here you can see the exit hole in the end of the cocoon (which is largely composed of caterpillar hairs).

And here it is! The Isabella Tiger Moth, Pyrrharctia isabella. A large, fairly attractive brown moth.

Not too flashy, but nice.

There is one flashy bit: the red-orange femurs on the front legs. Hey, that’s interesting: looking at the Isabella moth pictures on BugGuide, most of them don’t seem to have those orange-red legs. And the ones that do were caught in places like Ontario, Massachusetts, and British Columbia. It looks like that marking occurs in the northern and western populations, but not so much as one goes towards the southeast.

And here’s its face, with its threadlike, white antennae showing clearly.

In a lot of their range they have two broods per year, with the first brood hatching around May and maturing by August, followed by the second brood that overwinters as caterpillars. I’m not so sure they do that here, though. It seems like our season is awfully short to get in two broods of such a large moth, and so far we haven’t seen any sign of young banded woolly bears running around in the summer. Well, if anything turns up, I’ll let everybody know.

[1] It’s true that this is no great mystery, it’s easy enough to look them up, after all. Still, there’s nothing quite like doing something for oneself, even if it has been done to death by other people.

5 Responses
  1. JennyW permalink
    May 23, 2012

    I love the beautiful red on the forelegs. A very nice surprise for an understated moth.

  2. May 24, 2012

    It tells you something about its visual acuity when the antennae go right across its eyes.

  3. May 25, 2012

    Regarding the eyesight, to be honest I’m not sure why night-flying moths like this one even *have* eyes. All the eyes seem to accomplish is to draw them to an untimely doom around streetlights.

  4. May 27, 2012

    the eyes are evolved. The street lights are a source of food and (to a bug) hopefully heat at night. And to know where to go to hide during the day. (helps them tell the difference between light and dark.) pretty simple. Like a maggot.

  5. Ash permalink
    July 7, 2014

    I caught one for little cousin three weeks ago and have been feeding it everyday…it’s just the last two days I have been home much so I his scared it might have died..then I saw this black fuzzy cocoon and so I thought to myself..I killed it …thank you for showing those pictures ..I hope it hatched soon.

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