Luna Moth

2014 May 21

On August 15, 2013, Joe (one of our graduate students) told me that he had seen a large, green moth downtown. From the description, I suspected that it was a Luna moth. I’ve been wanting to get pictures of a luna moth for this site for a long time. Unfortunately, by the time I got to where he had seen it, it was gone. But fortunately, he had taken a picture of it with his cellphone, which he kindly sent to me. And here it is:

And we see that it is, indeed, Actias luna, which is widely regarded as being one of the most beautiful moths in North America. They are related to the Cecropia and Polyphemus moths that I’ve had pictures of in the past. And, like them, the adults are only supposed to live for about a week.

The thing that concerns me, is that Joe found this in mid-August. This is awfully late in the year for adult giant silkmoths. They are supposed to emerge from their cocoons around here in late May or early June, so this one was something over two months late. I don’t know what happened here. The spring of 2013 was delayed by about a month, so that probably had something to do with it, but the giant silkmoths we had overwintered in our cellar that same year had emerged by June 24 (and even those were about a month later than when we found the cecropia eggs in 2011).

I’m kind of concerned that the Luna moths might have been excessively delayed in maturing in 2013. If they all emerged in mid-August, like this one, then they would only have had two months for the eggs to hatch and mature before their food trees (birch) lost all their leaves around October 15. The timing is awfully tight on this, our Cecropias in 2011 took just a bit over two months to go from egg to cocoon, and this was in full summer when it was hot enough for them to grow fast. if all the other local Luna moths emerged this late, I’m afraid that the winter of 2013-14 came too early and wiped them out.

With any luck, it will turn out that this one was just really late for some reason (maybe its cocoon was in an unusually cool place, or maybe somebody had the cocoon in their refrigerator for the winter and then didn’t remember to take it out until August). Well, I’ll keep looking. If all is well with them, then they should start emerging right . . . about . . . now.

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