It’s a bird! It’s a bug! What the heck is it?
Like most gardeners, Bob Matthews is sometimes startled by the sudden sound of a big buzzing “bee” with forked antennae and a fuzzy, fanned tail. “I typically hear them before I even see them,” says the retired University of Georgia entomologist and author of several books on insect behavior. “And then I look around in the flowers and, by golly, there it is working the blossoms, one after another. … If they’re working a flower and you have the chance to watch them stick their tongue in and out while they’re hovering in front of it, you can pretty well convince yourself it’s not a real hummingbird. But you’re not sure what it is.”
This mystery critter is neither a bee nor a bird. A member of the sphinx family—the winged insect featured in the 1991 film “Silence of the Lambs”—the hummingbird moth flies and flits just like its namesake, hovering while sipping nectar and, thanks to its rapid wing movement, humming. Half the size of the ruby-throated hummingbird, the agile moth can fly frontwards and backwards and dart as quickly as a real hummingbird.
“It would be very hard to get a video of one,” Matthews says. “It would be a real challenge.”
North America boasts four species of hummingbird moths, but the one most commonly found in the Blue Ridge is the clearwing. As its name implies, its wings are transparent, a characteristic that sets it apart from most patterned moths. Another close relative: the tomato hornworm, whose green caterpillars sometimes appear on tomato plants in summer. All sphinx moths, incidentally, are known to rear their front ends up and coil them back, resembling the mythical Egyptian creature.
Not only are hummingbird moths totally harmless, they’re welcomed in gardens as major pollinators of tubular blooms such as bee balm, phlox and salvia. (Unlike hummingbirds, they’re not particularly drawn to red flowers.) The moth’s long tongue, which it carries rolled under its chin, stretches about twice the length of its body and can reach the base of a chosen flower.
“A typical pollinator bee has a very short tongue,” says Matthews. “So unless it can crawl down the tube, it can’t get at the nectar.”
Unlike most of their cousins, hummingbird moths are seldom active at night. They also tend to return to the same plants, day after day, at about the same time. For example, says Matthews, “They learned yesterday at 10 [a.m.] there’s some nice salvia over at Mr. Jones’ garden, and at 2 [p.m.] they discovered a patch of bee balm in Mr. Smith’s garden across the street. So the next day at the same hours, [they’ll] be in the same general area, searching for those nectar plants.”
Hummingbird moths live only six weeks at most, compared to real hummingbirds, which can survive for more than five years. In the Appalachian states, two generations emerge from cocoons each summer, the first in June, the second in August or September.
“It’s pretty remarkable to have an insect and a bird, two totally different animal groups, come to look so similar and behave so similar to each other,” Matthews says. “It’s almost a classic case of convergent evolution with the hovering ability and the ability to fly backwards and forwards. There aren’t very many insects that can do that, that are that agile. And there aren’t very many birds that are that agile either.”
The story above first appeared in our July / August 2022 issue.
