Polyphemus Moths

2014 October 8

Our neighbors across the street found this fine Polyphemus caterpillar on their back porch on September 2, 2013. We’d actually seen one of these before, but hey, one can always use more pictures of giant silkmoths, right?

When it felt threatened, it would scrunch up to about 2/3 of its original length.

Since we’d had good luck overwintering giant silkmoths the previous year, we decided to try again with this one. So, once again it made its cocoon in a nest of dead leaves, and we put it in our unheated cellar for the winter.

And, we brought it back out in the spring, and put the cage on the shady spot near the north porch to wait. And she popped out of the cocoon on June 27, 2014. A fine, fat specimen.

And I say “She” because this time, we actually got a female, as we can see both from her large body size, and from the fairly subdued feathering of her antennae.

Compare this with the feathering of a male Polyphemus moth antenna:

And where did I get the male moth for comparison, I hear you ask? Well, it’s like this. We put the cage with the female moth in it out on the north porch in the evening, and when we came back in the morning, all the guys had come around to check her out.

Including the ones that were just generally in the vicinity, there were nine males that came by. I understand that male giant silk moths can scent a female from up to two miles away, so they might have come a long way.

So, I got a few more pictures of adult moths, and then put several of the males into the cage with the female in hopes that they would mate.

An interesting feature about their wing coloration is that the center of the eyespots is not black – they are transparent. There are simply no scales in the eyespot centers, and the base wing is clear just like in most other insects.

So, anyway, after about a day, the female laid a bunch of eggs inside the cage, and then we let all the adults go. Here’s what the eggs looked like.

I had great hopes of raising up a bunch of polyphemus caterpillars from eggs, but sadly it didn’t work out. For whatever reason, the eggs never hatched. I don’t know if it was too dry for them, or if for some unfathomable reason the female never actually mated with the males, or what. We never actually did see the female mating, and now I kind of wonder whether having multiple males in the cage was a mistake. Perhaps every time one of them tried to make his move, the others stopped him. I really have to check into this before trying again.

We haven’t found any more caterpillars this year, but we might be able to find cocoons if we hunt for them. After my last polyphemus moth posting, our friend Colleen pointed us to a song called “John’s Cocoons”, by Michael McNevin, and it pretty clearly explains the methods his older brother used to hunt for polymphemus moth cocoons in birch trees in the fall.

8 Responses
  1. October 8, 2014

    One of your best posts ever. Fabulous photography and I love how you captured nearly the entire life cycle. Outstanding! Borrowing a photo and linking.

  2. October 8, 2014

    Thanks, KT!

    Incidentally, I’ve been checking into why the eggs never hatched, and it turns out that Polyphemus moths generally don’t breed in captivity (although they will sometimes breed if fresh oak leaves are in the cage with them).


    Other giant silkmoths are evidently easier to breed, but even there it turns out that special methods may be needed.


  3. October 8, 2014

    Tim, are these moths native species, or were they imported back in the day (sometime in the 1800s, maybe?) to try to get an American silk industry started?

  4. October 9, 2014


    These are definitely native. There were some attempts to cultivate some of the native giant silkmoths to produce silk, and the Polyphemus moths are regarded as having the most potential of any of the native North American species. However, their silk is coarser and harder to dye than the silk from true silkworms, and also they aren’t as easy to rear in captivity.

    Unfortunately, as part of efforts to establish a North American silk industry, Etienne Trouvelot imported Gypsy moths to North America. Apparently there were problems with disease in the silkworms available in the US at the time, and Trouvelot had the idea that he could cross-breed gypsy moths with silkmoths to make a disease-resistant silkworm. We now know that this was a completely unworkable idea (gypsy moths and silk moths aren’t even particularly related to each other), but he didn’t know that. So, it was the Gypsy Moths that got imported in the 1800s in connection with the silk industry.

    And now, the parasites that have been imported to control gypsy moths have turned out to also have an appetite for giant silkmoths. Bah.

  5. October 9, 2014

    How odd that they won’t breed in captivity. I guess you just ruined the mood, you buzzkill you.

  6. October 10, 2014

    It sounds like one of the problems with breeding giant silkmoths in captivity is that the males find the females by scent, and if they are in a confined space where the scent gets trapped, there is no scent gradient and he can’t figure out where she actually is. Some people recommend putting the female outside in a cage with a small enough mesh to keep her inside, but large enough for any males that come by to mate with her through the openings. This is put up so that the wind can blow through it, dispersing the excess scent.

  7. October 10, 2014

    And now, the parasites that have been imported to control gypsy moths have turned out to also have an appetite for giant silkmoths. Bah.

    Hmm. I’m glad I saw one when I did; I bet the spray that municipalities use to control gypsy moth infestation also affectsgiant silkmoths.

    As for raising them in captivity, I wonder if a room-sized “cage” would solve that problem. I’m sure you guys wouldn’t mind swathing half your garage in netting in the interests of giving the species a boost.

  8. October 11, 2014

    You could probably solve the problem with a decent-sized aviary.

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