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4. Hummingbird Moths: Marvelous Masqueraders
by Stephen W. Kress
Hummingbird gardens are ideal places to watch for hummer look-alikes—the hummingbird moths. In a classic example of convergent evolution, these swept-winged, stout-bodied insects dine on flower nectar and pollinate flowers in a manner remarkably similar to hummingbirds. Like their avian namesakes, they can hover seemingly motionless, while tapping nectar reserves with their long, coiled tongue. Some species even have green backs, further adding to their hummingbird resemblance. Unlike hummingbirds, though, they are late risers, waiting until the sun warms their wing muscles to stir them into action.
Members of the sphinx moth family, this enormously varied group derives its family name from the caterpillars that can pull their forebody up into a sphinx-like pose. The caterpillars are known as hornworms because they have a long, harmless spine that arises menacingly from their back near their posterior. While most sphinx moths visit flowers at night, hummingbird moths (also called clearwings because of the transparent patches in their wings) frequent gardens in full daylight. At a distance, some black and yellow species resemble huge bumblebees; however, bees settle on the flower, descending into the bloom, while hummingbird moths feed in a tireless manner, seldom resting.
Hummingbird-moth caterpillars feed mainly on honeysuckle, hawthorn, snowberry, and viburnum, but different species have special taste preferences. The caterpillars transform into pupae, which are enclosed in well-hidden, dense brown cocoons formed on the ground under fallen leaves. Some pupae overwinter under leaves, transforming themselves into flying adults the following spring. Double- or triple-brooded species pass through the pupal stage in midsummer, emerging as adults in late summer and fall.
Taxonomists have struggled with this group, since the different species vary in appearance at different locations in their vast ranges, and even different broods in the same location may look somewhat different. It is now generally agreed, however, that there are four species of hummingbird moths in North America. Range can help to sort them out, but several species overlap and at first glance they look similar. All species have clear parts in their wings and the males have a dramatic anal tuft, often in varied colors. In northern climates, hummingbird moths appear in midsummer, while those in southern climates often have two broods, the first in midspring, the second in midsummer into late fall.
Stephen W. Kress is Vice-President for Bird Conservation of the National Audubon Society and Director of the Society's Seabird Restoration Program. He teaches ornithology classes at the Audubon Camp in Maine and for the Cornell Laboratory of Ornithology. Stephen guest-edited the Brooklyn Botanic Garden handbook Bird Gardens (1998). He is author of The Audubon Society Bird Garden, The Audubon Society Birder's Handbook, the Golden Guide Bird Life, and other publications on birds and their management.