Moth ID can be a total nightmare because of the large number of species and the subtle differences among them. While the Butterflies and Moths of North America (BMNA) website generally has many more photos than printed guides, browsing through them is a slow process that requires a fast Internet connection. Sometimes thumbing through one of the following printed guides is easier, especially in the field:
- “Peterson Field Guide to Moths of Northeastern North America,” by David Beadle and Seabrooke Leckie (2012), with nearly 1,500 species.
- “A Field Guide to Moths of Eastern North America,” by Charles V. Covell, with 1,300 species (published in 2005 by the Virginia Natural History Museum and available in the Rappahannock County Library Conservation Collection).
- “Caterpillars of Eastern North America” (Princeton Field Guides), by David L. Wagner, which includes photos of caterpillars and adults for 700 Lepidoptera species.
- “The Moth Book: A Guide to the Moths of North America” by W.J. Holland, a landmark reference published in 1904 and covering 1,500 species. Large for a field guide and with low-quality photo reproduction (at least in the more widely available 1968 Dover reprint).
In settling down to enjoy my favorite radio show, Science Friday — or SciFri, as its fans know it — last Friday (July 25), I was surprised to learn it was National Moth Week. The show included a segment with NMW’s cofounder, ecologist Elena Tartaglia.
As implied by the segment’s title, “Moth-ers Celebrate Less-Loved Lepidopterans,” moths do not get the love and respect butterflies receive. Moths tend to be the Cinderellas of the Lepidoptera world in part because most come in subtle shades of white, brown and gray, unlike the usually more-glamourous butterflies. And we humans tend to be diurnal, which means we don’t see them as often (at least not in the light).
Tartaglia whipped out some other pretty interesting moth facts — such as that there are 15 times more species of them than butterflies. However, they do share some of the same dining habits: With many species, the adults dine on nectar or fruit, pollinating plants in the process, while adults in other species feed on other, less appealing fare, such as carrion. Some adult moths don’t eat at all; they just breed and die.
Tartaglia talked specifically about the io moth (Automeris io), whose caterpillar was featured in SciFri’s photo of the week. The io is among the giant silk moths. Like many of others in the family, it sports huge spots on its rear wings that look like owl eyes, which likely evolved that way to scare off predators. (For more of the interview and links to the io caterpillar photo and other moth information, go to ScienceFriday.com and search “moth week.”)
Tartaglia suggested several ways to lure moths in to observe them, including turning on outside lights, hanging a sheet up to provide a needed resting place (which also makes them easier to see at night), using bait or any combination of these. While the recipes — some of which are available on the NMW website — vary, the key ingredients are generally rotting fruit, sugar and beer.
I tried a variation of “Dave’s Recipe for Moth Bait,” by Dave Small, which calls for a rich combination of overripe banana or peaches in heavy syrup, dark-brown sugar or dark molasses (or both), dark beer and dark rum (or both). Lacking some of the ingredients, I made a lighter version with an overripe white peach, white rum, an IPA, honey and natural sugar. I did strictly follow the instructions that the alcohol should be “tasted before to ensure freshness.” I’m sure the original would draw in more moths, since, with moths, the stinkier, the better.
While the bait should then be painted onto trees, preferably near a light, most of the ones around my house are protected by a tangle of briars and poison ivy. Instead, I painted the bait on the wall under my porch and deck lights, and left the lights on. (I later thought that perhaps that might not be healthy for the moths, since the exterior of my house is painted, although I doubt they ate that much and the rain the next night probably washed away what was left.)
In checking the “study areas” a little after dark, I found a dozen or so small moths in various shapes and colors, including a gorgeous little ailanthus webworm moth, with its orange, black and white wings tightly folded, and a Eudryas grata (“beautiful wood-nymph”), which looks like a tiny plush toy with furry leggings. Another pretty moth — a delicate-looking, silvery one — will likely be a challenge to identify, so I saved that chore for later.
I was hoping to see one of the giant silk moths, such as the earth-toned io or prometha, or the lovely luna. The luna, with its graceful, delicate shape and minty green coloring accented with reddish-brown or yellow, “is regarded by many to be North America’s most beautiful insect,” according to the Princeton Field Guide “Caterpillars of Eastern North America.”
When it comes to size, however, the earth-toned cecropia moth (Hyalophora cecropia), with a maximum wingspan of about six inches, takes the prize. Although judging size is problematic, since wingspan or wing area are often used for that purpose, the cecropia is the largest according to most sources, though the specific wingspans listed for other moths may be greater.
In any case, the saturniidae are all pretty darn impressive, although they are actually not the largest moths in the world. While sources vary, Texas’ white witch moth (Thysania Agrippina), in the Noctuidae family, seems to be duking it out with the atlas moth (Attacus atlas), another saturniid, from southeast Asia, for the title of largest lepidopteran. I bought a mounted specimen of an atlas moth at auction a few years ago that has a wingspan of 8.5 inches, and that’s a small one. The wingspans of both of these behemoth moths can reach almost a foot.
The night I tested the bait, the only saturniid I attracted was a regal (a.k.a. royal walnut) moth (Citheronia regalis), and it came in because of the light, since adults don’t eat. Its wingspan was about four inches, which means it’s likely a male, since females are bigger, with wingspans up to 50 percent wider. Although basically brown, like many moths, it’s set off by yellow spots and orange veins.
Identifying moths can be challenging — in great part because the photos included in most guides are of dead ones, with their wings neatly spread out so the dorsal markings on both the fore and hind wings are visible. In many species, the hind wings have the most distinctive markings. Live io moths, for example, will spread their wings when disturbed, flashing the “eye” spots at potential predators. But, like many species, the io keeps its hind wings folded under and hidden when at rest, so comparing the photos in a guide to the live moth is problematic.
For the little wood-nymph on my deck, the most distinctive point was its furry legs, which do not appear in the spread-winged photos in my guides. And, with the wings tightly folded, the scalloping in their white portions, which distinguishes this moth from the pearly wood-nymph (its smaller cousin), was difficult to make out.
No matter how challenging moth ID can be, celebrating the glory of these lepidopterans is always worthwhile. With or without the bait, just leave a light on outside and check often for visitors. But be sure to turn off the light when you’re done, so the moths can get back to work procreating and pollinating.
© 2014 Pam Owen