Aquatic Insects of Michigan
by Ethan Bright, Museum of Zoology Insect Division and School of Natural Resources and Environment
Calopterygidae (Broad-winged Damselflies) of Michigan - Identification
Four species in two genera of this primarily tropical family damselflies are found in Michigan. These are large, beautiful damselflies that are often seen flying among our streams and rivers in Michigan. Adults have mating behavior involving conspicuous competition among males for territory and females. Nymphs usually are quite large,narrow-bodied with thick, large caudal gills. The elongate first antennal segment and large premental cleft is clearly distinctive from all other damselfly families. Common in streams and rivers, nymphs cling to leafy or woody debris or among aquatic vegetation along accumulating along banks. Older literature refers to this family as Agrionidae.
Calopteryx Leach, 1815 (Jewelwings) are some of our prettiest odonates, with conspicuous green to blue metallic bodies with often black or black-marked wings. Widely distributed in temperate North America and Eurasia, the two species found in Michigan - C. maculata (Beauvois, 1805)(Ebony Jewelwing) and C. aequabilis Say, 1839 (River Jewelwing) - are widely distributed throughout Michigan. Both species of these very large damselflies are quite common in streams and rivers. Nymphs are most frequently found among woody debris and rootlets of vegetation, to which they cling, in streams and river sections with adequate current. Whereas C. aequabilis tends to be found in larger streams and rivers with more open vegetation, C. maculata is commonly encountered in smaller streams in shaded, forested areas, though there is some overlap and both species sometimes are conspecific. The latter species tends to be more commonly encountered in our state, though both are found throughout the state. Life history of nymphs for both species in Algonquin Park, Ontario was studied by Martin (1939). She found C. maculata to be univoltine, C. aequabilis semivoltine and requiring two or more years to complete development. In terms of growth rate, that of C. aequabilis tended to be greater than early on, then decreases, whereas that of C. maculata increases with maturity. Females required more time to mature than males. Very early instars of the two species were distinguishable based on the head width and length of the proximal antennal segment. I (EB) have seen adults of C. maculata on wing in early May in southern Michigan (Black Creek, tributary of the River Raisin, Lenawee Co.) as well as C. maculata and C. aequabilis through mid- to late-June (Mountain Stream, Huron Mountains, Marquette Co.). Their intricate mating behavior, particularly that of male territoriality and mating rituals, has been the focus of much research wherever this genus occurs (e.g., Walker 1953, Johnson 1962, Waage 1973 and Conrad & Herman 1987).
Hetaerina (Rubyspots) are large stream damselflies most numerous in Central and South America, but only four species reach the United States and only two reach Michigan in the south. The two species of Hetaerina recorded from Michigan - H. americana (Fabricius,1798) (American Rubyspot) and H. titia (Drury,1773) (Smoky Rubyspot) - are darker, with clearer wings with conspicuous red basal marks. Records of H. americana are known only from the LP, though it appears widespread there. One well-established locality in Livingston County exists for H. titia, and it appears conspecific with H. americana (Weichsel 1987, 1998; pers. obs.). Another old literature record exists from Oakland County (Kormondy 1958). Since then, other records have been record from southeastern Michigan. Larvae are similar to Calopteryx in habits, frequenting the edges of gently flowing streams and rivers wherewhere woody debris, leafy matter or sometimes where dense macrophytesaccumulate (Westfall and May 2006; pers. obs.). Hetaerina adults tend to emerge later in the year (mid-June through mid-July) than species of Calopteryx (late May through June), though Weichsel (1987) indicates that adults are on-wing as early as late-May. I (EB) have seen large numbers of exuvia in the third week of June (1996) from upstream River Raisin in southeastern Michigan (Jackson County). Adults emerged enmass from a quiessent part of the stream thick with aquatic vegetation that protruded from the watersurface. The UMMZ collection of adult Hetaerina - thanks to years of work by E. B. Williamson, E. J. Kormondy and L. K. Gloyd - is probably the most extensive in the world. Zloty et al.(1993) used Cellulose Acetate GelElectrophoresis to associate larvae and adults of Costa Rican Hetaerina in order to construct a diagnostic key, a method with much future promise in distinguishing groups with similar-appearingspecies.
Family Diagnosis: Broad wings, numerous antenodal crossveins between costa and subcosta instead of two, as in other families; dense ventation; postnodal crossveins not in line with veins below them; anal vein at its base is separate from the hind margin of wing, and thus wings are not petiolate; quadrangle is long, nattow, and parallel-sided, with several crossveins; pterostigma poorly developed, without brace vein; males, and often females, pigmented, body color is metallic; nymphs large, long-legged, stiff-looking insects clinging to roots, stems, and other extending substrates at stream edges; head flat, pentagonal, first antennal segment elongate and longer than other six segments combined, often longer than head; prementum produced and having a deep, diamond-shaped cleft; palpal lobes of labium end in 3 curved, acute processes; caudal gills are long and stiff, with long setae, sometimes interspersed with stout spines.
Taxonomic References: Paulson 2011, Tennessen 2006, Walker 1953, Westfall and May 2006
Key to Adults
Key to Mature Nymphs
Beauvois P de. 1805. Insectes recuilles en Afrique et en Amerique dans les royaumes d'Oware, a Saint-Dominique et dans les Étais-Unis pendants les années 1781-1797. Levrault: Paris. 167 pp.
Page last edited: March 1, 2017 (EB)