Two genera of this primarily tropical family damselflies are found in Michigan. Mature specimens usually are quite large, and the elongate first antennal segment (picture) and large premental cleft (picture) is clearly distinctive from all other damselfly families. Common in streams and rivers, larvae are primarily found along banks with accumulations of leafy or woody debris or among aquatic vegetation. Adults, noted for their rather large size and beautiful colors, emerge in late spring (Calopteryx) and early summer (Hetaerina). Older literature refers to this family as Agrionidae.
1a. Prementum cleft long, nearly halfway to its base (picture1, picture2); posterolateral margins of abdominal segments 9 and 10 without spines - Calopteryx
1b. Prementum cleft short, reaching only to base of palpal lobes (picture); posterolateral margins of abdominal segments 9 and 10 with small, distinct spines (picture) - Hetaerina
Walker, E. M. 1953. The Odonata of Canada and Alaska, Vol. 1. University of Toronto Press: Toronto, Ontario. xi + 292 pp.
Westfall, M. J., and M. L. May. 1996. Damselflies of North America. Scientific Publishers: Gainesville, Florida. x + 650 pp.
Westfall, M. J., and K. J. Tennessen. 1996. Odonata, pp. 164-211. In An Introduction to the Aquatic Insects of North America, 3rd Ed. Merritt, R. W. and K. W. Cummins (eds.). Kendell/ Hunt Publishing Company: Dubuque, Iowa.