An Interview: NH's Giant Silk Moths
Have you been lucky enough to see giant moths flying around in colorful outfits? Or perhaps huge caterpillars wandering about? Many of these moths are in the giant silk moth family Saturniidae and we have four particularly large and noticeable species in our region, the Luna, Polyphemus, Promethea and Cecropia.
I interviewed Sam Jaffe, director of The Caterpillar Lab in Marlborough, NH about these amazing creatures. While the Lab is currently closed, Sam’s website www.thecaterpillarlab.org and Facebook page www.facebook.com/thecaterpillarlab are amazing resources to learn more about these moths and many other caterpillars. Once the Lab is open again, it is a great place to visit.
Amy: Hi Sam, I wanted to talk to you about the giant silk moths. I recently saw a Luna moth in my garden and thought people might be curious about these spectacular moths.
Sam: It is so wonderful that these giant silk moths can be backyard creatures here in New Hampshire. What a great find! Luna moths in particular have been having a banner year and people are just happening upon them. Mostly the adult moths are seen under porch lights in the morning, but this year we are getting many reports of them in gardens and along trail sides. Now that the adult’s season is coming to an end, people are starting to find their plump green caterpillars around. I’d bet you have some quietly munching Luna caterpillars around the edge of your yard.
One of my favorite things about this group of jumbo moths is their ability to surprise people and make them reconsider what wild things might be present around them here in New England. So many naturalists and nature lovers that I have spoken with can trace back their interests to discovering a huge Cecropia or Luna by accident and just being blown away. I bet some people reading this interview can remember such a moment too.
Amy: Are there some general characteristics about this Family?
Sam: No single feature easily defines the silk moth family Saturniidae, but taken together some characters can help you identify one. Giant silk moths are often some of the largest moths in an area. They don’t feed as adults, so they have no obvious tongues and won’t be found at flowers. They tend to have broad feather-like antennae, broader in males than females. They are very fluffy, with thick hairy legs, and many have false eyespots and bright colors. Here in New England there aren’t so many species so you can also just try to learn them all, so you never miss one! At my moth lights, I see the four giants Luna, Polyphemus, Promethea, and Cecropia, as well as smaller members of the family like the Io, Buck Moth, Pink-striped Oakworm, and the smaller but adorable Rosy Maple Moth.
Most giant silk moths fly as adults from May to early July, feed as caterpillars through the summer and into the early fall and overwinter as pupae wrapped up in silken cocoons. The Oakworms and Rosy Maple Moths are a bit different as they overwinter as pupae in the soil with no cocoon. The Buck Moth has a very different life history, flying in the fall and overwintering as eggs.
Amy: Can you describe a little about each of the species and where and when people might see both the caterpillars and adults?
Sam: There is so much to say about each! But I’ll try to keep it short, so I don’t overwhelm everybody…
The Cecropia, Hyalophora cecropia is a monster moth, both as an adult and a caterpillar. The adult is often cited as being the largest flying insect in North America. It has brilliant red, purple, gray, and white coloration with false eyespots on its wingtips. I can’t imagine anyone encountering this species without being struck by its size and beauty. The caterpillar is also gargantuan. It is New England’s largest caterpillar and easily reaches the size of a breakfast sausage. In addition, it is very colorful with red, orange, blue, and yellow bobbles all over its green body. In New Hampshire, the moths tend to fly through the end of June and the caterpillars are found in July and August. The caterpillars eat a range of woody plants but especially love Cherry, Apple, Walnut, Buttonbush, and even the invasive Glossy Buckthorn.
The Promethea, Callosamia promethea, is rather like a smaller version of the Cecropia. This species is sexually dimorphic, meaning the males and females look different. Females are various shades of brown and red with broad wings, while males are very dark brown with more elegant, narrow wings. The males actually fly during the afternoon and evening looking for females that call them in with a pheromone, or scent, that they release into the air. Females fly during twilight and after dark, searching out places to lay their eggs. The caterpillar is sizable, though nowhere near as big as a Cecropia. It is plump, almost white, with waxy, bright red and yellow horns. In New Hampshire, the adults are active from May through July and the Caterpillars are most common from July through early September. Caterpillars specialize on a few host plants including Black Cherry, Ash, Sassafras and Spicebush, and occasionally garden planted Magnolias.
The Polyphemus, Antheraea polyphemus, is a big, tan, and beautifully eye-spotted moth. They are sometimes confused with Cecropia, but are slightly smaller and not as colorful. Still, those blue false eye spots on their hind wings can take your breath away. Polyphemus are expertly camouflaged when at rest with their wings closed – they look just like a dead leaf. But when disturbed, they flash those big false eyes and surprise predator and unprepared human alike. Polyphemus caterpillars are big, plump, and bright green. They are quite similar to Luna caterpillars and often confused with them. In New Hampshire, adult Polyphemus moths can have a long flight season from May through early August and caterpillars are especially common in August and September. Caterpillars eat a broad range of woody plants but are most common on Oak, Gray Birch, Black Cherry, Amelanchier, and Beech.
The Luna, Actias luna, is perhaps the most famous giant silk moth in North America. It is huge, luminous, bright green, has delicate false eyes, and long twisting swallowtails. It really is stunning. The tails are thought to be used as a defense against bats. As a Luna flies through the woods, the twisted tails constantly change their orientation and confuse incoming bat sonar/echolocation so that bats have a difficult time pinpointing a Luna’s location! The caterpillars are plump, bright green, and look a lot like a Polyphemus caterpillar. One helpful feature to tell the two apart is to look at the caterpillar’s face. If it is reddish brown and has a beard of hairs it is a Polyphemus; if it is green or occasionally dark brown with very few to no hairs, it is a Luna. In New Hampshire, the moths generally fly only in May and June, though this year they are still showing up at my lights in late July! The caterpillars are most common in July and early August. Luna caterpillars specialize feeding on Gray and Paper Birch in this area, but also enjoy Hickory, Walnut, and Black Gum where available.
Amy: Is there anything you would like to add to wrap this up, Sam?
Sam: I just want to let everybody know that we are VERY lucky to have these moths here. In many areas of New England, the giant silk moths have declined or even disappeared. They are sensitive to so many of the changes we impose on environment. Pesticides and light pollution can destroy moth populations in cities, suburbs, and around some agricultural areas. Climate change and shifts in host plant availability may also be taking their toll. And in what may be the most serious threat to them, some non-native parasitic flies kill off a large percentage of them each year. Sadly, two incredible species of giant silk moth are now extirpated, or have gone locally extinct, in New England: The Imperial and Regal Moths. The best thing we can do to ensure that these beautiful, magnificent, inspiring insects continue to survive here is manage invasive plants and maintain natural habitat, plant native plants in our gardens, and decrease light pollution. We also must consider our use of generalized pesticides carefully, with all the knowledge of what broader effects their use may have on our local environments and critters.
I hope everybody has a chance to meet some of these jumbo moths! Thanks Amy for thinking of the moths and The Caterpillar Lab for this article!
Interview & Article by: Amy Bodwell
CCCD Board Vice-Chair