Hummingbird Imposters

By Janet Sternburg | June 2, 2001
From Missouri Conservationist: Jun 2001

Every summer people call or write the Conservation Department to report seeing an animal that looks like a hummingbird, flies like a hummingbird and eats from flowers like a hummingbird. But then they say it can't be a hummingbird because it has antennae.

Well, here's some good news. There is an insect that looks and acts like a hummingbird and is even named after a hummingbird. It's called a hummingbird clearwing, and it's one of 125 moths in the sphinx or hawk moth family (Sphingidae) that inhabits North America. Of these, 56 live in Missouri. About 975 other species are found throughout the rest of the world.

Sphinx moths get their name from the posture their larvae assume when disturbed. The larva elevates the front part of its body and assumes a Sphinx-like posture. The larvae of many sphinx moths are known as hornworms because of the horn- or spine-like appendage on the last segment of the body.

Hawk moths are another group in the family, but the name also is used interchangeably with sphinx moth. Hawk moths are so named because of their swooping flight.

An adult sphinx moth has a protruding head with large eyes, a large, "furry" thorax-the middle body segment where the wings are attached-and a conical abdomen that extends well beyond the hind wings when the moth is flying. The front wings are long and narrow, and the hind wings are smaller. Sphinx moths fly with strong and rapid wing beats and are among the few groups of insects that can hover. People also sometimes mistake the white-lined sphinx for hummingbirds. This species is common in Missouri. The white-lined sphinx is active primarily between dusk and dawn, but occasionally people spot them during daylight hours.

Clearwing moths, the group to which the hummingbird and bumblebee mimics belong, lose the scales on their front wings after their first flight. Their wings resemble leaded stained glass with clear glass in the panels, much like a bee or wasp wing.

The snowberry clearwing is often mistaken for a bumblebee. Not only does this clearwing have yellow and black bands, it also hovers and flits from flower to flower while sipping nectar. Clearwings are active during the daytime when people are most likely to see them.

Adult sphinx moths are medium to large moths with wingspans ranging from about 1.25 inches to 4.75 inches. The snowberry clearwing is one of the smallest moths in this group, while the five-spotted hawk moth is one of the largest. Its larva is the familiar tomato hornworm. The Carolina sphinx, whose larva is known as the tobacco hornworm, weighs only one to two grams, but it flaps its wings an astonishing 25 to 30 beats per second. Some sphinx moths have been clocked at speeds as high as 30 mph.

Sphinx moths are often mistaken for hummingbirds and bumblebees because of their similarities in size, foraging behavior and feeding structures. Most sphinx moths are active between dusk and dawn, but several species are diurnal, meaning they are active during the daytime when hummingbirds and bumblebees are also out and about.

When flying, the clearwing moth makes a buzzing sound with its wings, similar to that of a hummingbird. Like hummingbirds, most sphinx moths fly in a quick, darting manner and hover over flowers while sipping nectar. Although sphinx moths sometimes land on a flower while feeding, hummingbirds almost never do. This is a good clue to determine if you are seeing a moth or a bird.

Adult sphinx moths have a long, straw-like "tongue," called the proboscis, which they keep curled under the head. They use it to suck nectar from the flower. The nectar is rich in sugar, which fuels the energy required for hovering. Hummingbirds also have a long tongue to lap up nectar. The length of the proboscis roughly equals the length of the flower tube from which the sphinx moth is eating.

Several sphinx moths have very small mouth parts that are almost useless. These moths feed very little as adults or perhaps not at all. Movie fans might be familiar with one of these sphinx moths, the death's head moth, which was mentioned in the film Silence of the Lambs. This European sphinx moth is named for the skull-and-crossbones pattern on its furry thorax.

Moths, including sphinx moths, pollinate many species of plants. Moth-pollinated flowers tend to have a strong, sweet scent and are white or pale in color. Gardens planted with these flowers may attract several kinds of sphinx moths, including the hummingbird and bumblebee mimics.

While eating the nectar of a flower, moths receive a dusting of pollen by brushing against anthers, which produce pollen. Their fuzzy bodies are excellent pollen carriers. As a moth sips nectar from another flower of the same species, it transfers pollen from the previous plant. This cross-pollination is necessary for many species of plants to produce seeds.

The hummingbird clearwing is relatively common in Missouri. Adults may be found in the daytime in open woodlands and fields and in gardens and suburbs throughout the state between early April and September. This moth is reddish brown and has a wingspan of about 1.5 inches to 2.25 inches. Its larvae feed on honeysuckle, buckbrush, wild cherry and plum. Adults hover and sip nectar at many different flowers, including honeysuckle, beebalm, phlox, lilac and blueberry and milkweed.

The snowberry clearwing is relatively common in Missouri. Adults fly throughout the day in open woodlands and fields, as well as in gardens and suburbs throughout the state, between late March and September. This bumblebee mimic is yellow with black wings and abdomen. At 1.25 to 2 inches, its wingspan is slightly smaller than that of the hummingbird clearwing. Its larvae feed on honeysuckle, dogbane and buckbrush. Adults eat from many flowers, including thistles, milkweed and lilac.

The white-lined sphinx may be observed flying day and night in open habitats including woodlands, fields, gardens and suburbs throughout the state between early April and November. The top of its fore-wing is dark olive brown with a narrow tan band running from the base to the wing tip and with light tan streaks along the veins. Its wingspan is about 2.5 to 3.5 inches. The white-lined sphinx is common in Missouri. Its larvae feed on many plants, including purslane, willow herb, evening primrose, elm and tomato. Adults feed at a variety of flowers, including honeysuckle, columbine, moonvine, lilac, Jimson weed, larkspur and petunia.

In addition to clearwings and white-lined sphinx moths, there are dozens of other sphinx moths in Missouri. These moths are sometimes seen flying around outdoor lights or-at dusk-sipping nectar from petunias, moonflowers, phlox, bouncing bet, honeysuckle, morning glory and primrose.

The most species of sphinx moths I have ever seen in one place was six. I saw them along a busy road in Branson at dusk as they visited a flower box containing many different varieties of petunias.

If you happen to see a hummingbird or a bumblebee this summer that doesn't look "quite right," don't call your eye doctor. Your eyes are fine. You probably just saw a hummingbird or bumblebee clearwing, or a white-lined sphinx moth. It's an imposter, but one you can enjoy observing.

This Issue's Staff

Editor - Tom Cwynar
Managing Editor - Bryan Hendricks
Art Editor - Dickson Stauffer
Designer - Tracy Ritter
Artist - Dave Besenger
Artist - Mark Raithel
Photographer - Jim Rathert
Photographer - Cliff White
Staff Writer - Jim Low
Staff Writer - Joan McKee
Composition - Libby Bode Block
Circulation - Bertha Bainer