Back in June a friend sent me a picture of the tremendous Luna Moth that she saw on a tree trunk near Sawyer Pond in Gilmanton.
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| Luna Moth (Actius luna), June 21, 2020. (Photo by a good friend.) |
These are one of our largest moths and though not rare in New Hampshire, they are not often seen due their nocturnal behavior. I still remember the first time I saw one of these - it was on the exterior wall of my parents cottage on the west side of Lake Wicwas. My mom noticed it and called us all out to see it. I don't know if it was her excitement or just the size and beauty of it, but that moment has stuck with me, and I've been fascinated by them ever since. I haven't seen one myself in a long time so I was most appreciative of receiving this photo from a friend - thank you!
Luna moths are members of the silk moth family, and are found only in North America. They are sensitive to light so are often attracted to porch lights. But this attraction to artificial light is also a problem for them as it affects their navigation and possibly their life cycle. Light pollution and pesticides are two of the largest risks to these moths, as are naturally occurring parasitic flies and the many birds and animals that hunt them for food. Their attraction to porch lights and their subsequent landing on illuminated walls makes them highly visible to predators.
I'm writing about the Luna moth now because Linda found this huge green caterpillar crawling along the ground in one of her gardens this week, and we immediately thought "Luna moth".
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| Polyphemus moth (Antheraea polyphemus) caterpillar. |
Researching this journal entry I learned wasn't a Luna moth caterpillar, but rather a Polyphemus moth caterpillar. The Polyphemus moth is equal in size to the Luna, but its adult form is brown rather than green, and it also has the distinctive eye shapes on its wings which help to confuse and scare predators. The two moths' larval stages are very similar; I learned the best way to distinguish them is by their face. The Luna moth has a green face while the Polyphemus moth has a brown, bearded face. Fortunately we had gotten a good look at its business end.
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| Linda's friend has the brown face of the Polyphemus moth. |
This future-moth will soon wrap itself up in a cocoon made of silk and leaves where it will spend the winter amidst the leaf litter - another reason not to rake the leaves under the trees at the periphery of your lawn!
Both types of these "macro" moths have one life cycle per year. The pupa will start to develop in May when the ground warms; the adult moth will emerge a few weeks later. The adult does not eat, but will find a mate and the female will lays its eggs on the underside of a leaf - mostly birch in our area, but hickory and walnut are also preferred hosts. The eggs will hatch in about a week and eat and grow until they reach three inches in length. During this phase both Luna and Polyphemus caterpillars will molt five times as they grow; each of these phases is called an "instar", so these species have five instars. After their final instar they will form their cocoon and the cycle begins again. Here are a couple of references to learn more about these giant insects:
These caterpillars will be all sealed up and safe when the cool weather arrives. Did you feel the late-summer chill in the air earlier this week? The lakes sure did, and they showed their displeasure by weeping mist from their still-warm waters.
Summer is starting to get tired.
Thanks so much, Scott for the primer on the Luna moth which I also love. We also found a large green caterpillar in the leaves in our woods. I did not see the ends so I do not know which moth it is to be. But now I know why it was in the leaves.
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