I found one of the culprits that can cause cucumber wilt on some milkweed plants in a backyard nearby yesterday — the very attractive orange and black Squash vine borer moth (Melittia cucurbitae). It’s too bad they are such damaging pests in the garden because they are quite photogenic.
Long, highly “feathered” back legs drag behind the body as the moth flies, making it look like the wasp that it is trying to imitate. But the clear, moth-shaped wings give it away, although these are not really visible to the human eye because they are moving so fast, they almost disappear.
Many of the species in the Sesiidae family are active in the daytime and are brightly colored, yellow and black or orange and black, mimicking bee or hornet coloration. This Batesian mimicry (in which a palatable species mimics an unpalatable or predatory one) presumably reduces their chances of being eaten by predators while foraging on flowers in the daylight.
Other members of the Sesiidae family are also agricultural pests, infesting fruit tree, vegetable, and timber crops, as their larvae bore into the woody stems or trunk and decimate the interior vasculature system of the plant.
The Clearwing Hummingbird Moth (Hemaris thysbe) is no relation to the garden villain above. It’s a member of the Sphingidae family of hawkmoths, and although the larvae do feed on honeysuckle vines and some fruit trees, they don’t do nearly the damage that the Sesiidae species do.
I’m not sure what the significance of clear wings is in these very different clearwing moth species. Perhaps lack of scales on the wings means less air resistance during hovering flight, which both types of moths use for nectar foraging; or perhaps clear wings enhance their mimicry; or perhaps clear wings just present a smaller target to potential predators, since they appear almost transparent while the moth is flying. Whatever the reason, the convergence of species from two different moth families is an interesting one.