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A case of mistaken identity

It happens every year around this time almost like clockwork. The phone rings, an Email arrives, or the subject simply arises during the course of casual conversation. Some person tells me how he or she saw this beautiful, striped hummingbird feeding on nectar in their flower garden. Its certainly not the only case of mistaken identity I hear of but it is perhaps the surest bet. For the next several minutes I carefully explain what the individual witnessed was actually a cool insect called a White-lined Sphinx Moth (Hyles lineata) and not a hummingbird.

According to Dr. Gerald Fauske, NDSUs collection manager of the state insect research laboratory, there have been 37 species of Sphingidae (sphinx family) recorded in the Dakotas. The family is so named because of the caterpillars habit of rearing up in an aggressive posture when threatened. They kind of curl up like a question mark, said Fauske. Along the way, he said, someone thought this resembled the Egyptian sphinx.

Collectively they are also known as hawk moths or hummingbird moths. One sphinx from Europe, the deaths head moth, was made famous in the movie Silence of the Lambs. It sports a skull-and-crossbones pattern on its back. But its the White-lined Sphinx that so mimics the habits of hummingbirds that it is frequently thought to be one.

The larva, or caterpillar stage, of this moth is rather large and hairless. It is mostly green with varying amounts of darker barring. Most prominent is its single horn protruding near its rear end. Some plants the caterpillar is known to feed on include tomato, potato, and evening primrose. Most area gardeners have probably run across them.

The insect cannot tolerate our winters so are blown here every spring on southerly winds. They arrived this year at the end of May. Fauske called this, exceptionally early. The adult moth has a brown head, a brown thorax with six white stripes, and a brown abdomen with symmetrical dark spots. The wings are boldly patterned in dark and light hues, with the rear wings displaying much pink.

While it is encountered during daylight hours this insect is more associated with a dusk feeding schedule that will continue into the night. The moths size and rapid wing beating lets it feed in a style very similar to hummingbirds, through hovering. But this flight habit means quite a bit of energy is required and much heat is produced. For this reason the moth must feed on nectar sources high in sugar. These include such flowers as petunia, honeysuckle, lilac, clover, and columbine.

The White-lined Sphinx Moth is among the largest local flying insects and reaches sizes comparable to our resident hummer, the Ruby-throated Hummingbird. While flying, the moth even gives off an audible hum similar to a hummingbird.

Given these parallels, it is not difficult to make the mistake of calling the moth a hummingbird. So how do we distinguish between the two?

First, consider the time of day. Hummingbirds are encountered during daylight hours while the White-lined Sphinx Moth is typically seen at or near sunset (but not always). Second, there is no hummingbird in North America that is striped. The moth should display bold stripes in flight whereas a hummingbird should appear to be mostly green. If a close enough look is allowed, one should be able to see antennae on the moththe hummingbird will have none. Check also for its tongue. Quite often an observer will notice a long tongue sticking into the flowersthis again will be the moth. Finally, the White-lined Sphinx will, quite commonly, sit on flowers while feeding, something hummingbirds rarely do.

Armed with these hints one should, with some accuracy, be able to distinguish between hummingbirds and White-lined Sphinx Moths. While it is always thrilling to see a hummingbird feeding, be aware that there is an insect imposter waiting to sample your flower nectar too. But we really cant lose either wayboth are worth looking at and enjoying.