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Male Damselfly Identification

A few species of damselflies are distinctively colored, but many more, such as the bluets, genus Enallagma, have very similar colors and patterns. Field identification with binoculars is sometimes possible. There are times, however, when catching them for close study in the hand is the only way. Such close familiarity in the hand also makes binocular identification a lot easier!

DAMSELFLIES OF NORTH AMERICA, by Westfall and May, is the best source for damselfly identification. The Maryland species, with a handful of exceptions, are well covered in Dunkle's DAMSELFLIES OF FLORIDA, BERMUDA and the BAHAMAS.

The key anatomical features to check on male damselflies are the terminal appendages, located at the end of the abdomen. The cerci and paraprocts, especially in side view, are diagnostic. (Viewed from above, there are two cerci , one on each side, and two paraprocts below them, one on each side.) With most eastern species a simple hand lens is quite sufficient. When catching them, remember that the newly emerged tenerals are too soft to handle safely, and the structures might not be fully expanded. With adult males, keep in mind that the cerci and paraprocts are actually complicated three-dimensional structures. The drawings here are in side profile. If you you are holding the damselfly such that it is not perfectly in side view, the structures appear very different, and will not look like the drawings. Some individuals may also be damaged.

Where are the females? The most useful anatomical structures for the females are the mesostigmal plates, near the "shoulder". These are well illustrated in Westfall and May. They can sometimes be studied with a hand lens, but usually a microscope is necessary for positive identification. Like the males, many females have distinctive patterns on the thorax and abdomen, and can be identified in the field with lots of practice. For unusual records, however, capture is usually necessary.