Hine's Emerald Dragonfly
Listing. Hine's emerald dragonfly (Somatochlora hineana Williamson) is among the most endangered dragonflies in the United States. It was listed as state endangered in Illinois in 1991 (Illinois Administrative Code. 1992. Illinois List of Endangered and Threatened Fauna, 17 Illinois Administrative Code 1010. 1992. Illinois Register 16 (1):107), and was placed on the Federal Endangered Species List in 1995 as endangered (Federal Register, Vol. 60, No. 17, Rules and Regulations, p. 5267).
Description. The adult Hine's emerald dragonfly is distinguished from all other dragonfly species by the following combination of characteristics: its brilliant, emerald green eyes, dark brown and metallic green thorax with two creamy-yellow lateral lines, distinct terminal appendages of the male and ovipositor of the female. The wings are transparent with amber tinting at the base of the hind wing. Individuals tend to develop darker tinting on both pairs of wings as they become older. The wingspan ranges from 90-95 mm. The total length ranges from 60 to 65 mm.
The larva (nymph, naiad) is approximately 25 mm. in length and is light to dark brown when mature. The body is densely clothed with coarse setae (hair). The following measurements were taken from 4 final instar larvae and 33 exuviae (cast larval skins): hind femur, 6.8-7.6 mm.; hind tibia, 7.7-8.5 mm.; no. of palpal setae, 8-9; no. of mental setae, 11-15; largest dorsal hook on segments 7-8; dorsal hooks on segments 3-9.
Potential range, Historic localities, and present known distribution for the Hine's emerald. Hine's emerald was formally known to breed in selected wetland habitats in Ohio, but has not been observed there since 1961. This species was described in 1931 from seven specimens collected in Logan County, Ohio. It also was recorded from Lucas and Williams Counties (present in Lucas Co. until 1961). Other single specimens were recorded from Gary, Indiana (1945), near Scottsboro, Alabama, (1978), Will County, Illinois (1983), and Door County, Wisconsin (1987). From 1988 to 2012, many sites were surveyed by biologists primarily in Illinois, Wisconsin, Ohio, Michigan, and Missouri to locate breeding populations and to study the biology and ecology of this species. Breeding populations are now known to occur in northeastern Illinois in or near the Des Plaines River Valley, Missouri, Wisconsin, northern Michigan, and Ontario, Canada.
A recent report on potential Hine's Emerald habitats in Illinois is available in PDF format.
Biology. In general, adult dragonflies are terrestrial, spending much of their brief life in flight, feeding on other flying insects. The larva is aquatic, lives substantially longer than the adult, and feeds on other smaller aquatic invertebrates, small fish, and larval amphibians. After adults emerge, usually males later establish breeding territories and mate with females. Females lay eggs in suitable aquatic habitat.
Hine's emerald larval habitat appears to be cool shallow, slow-moving waters (usually only several centimeters deep), spring-fed marshes, and seepage sedge meadows. Most larvae have been found in shallow water of narrow channels, as well as along edges of channels. After adults emerge they spend a few days feeding before they return to breeding areas. Males then establish and defend breeding territories (small areas of shallow water) by hovering and pivoting over the water's surface. As females approach, males pursue and mate with them. On her return the female oviposits (lays eggs) by repeatedly plunging the tip of the abdomen into shallow water. Metamorphosis starts to take place as the final instar matures. Mature larvae crawl out of the water onto nearby plant stems or anything providing support. The skin splits on the back of the head and thorax, and the adult emerges, leaving the exuviae behind. After a few hours, the adult is ready to feed. Hine's emerald exuviae have been found along the edges of channels and as far as 3 meters into adjacent marsh. Exuviae have also been found in seepage sedge meadow. Larval habitat also includes sheet flow through spring-fed seepage marsh. The larval stage may extend from two to four years depending on local weather conditions. Larvae and possibly some eggs may overwinter. Recent studies have shown that larvae may survive drought periods and may overwinter in burrowing crayfish tunnels (pers. comm., Lauren Pintor). Newly emerged (teneral) adults have brown eyes which turn bright emerald green after a few days. Adults usually fly over open areas of herbaceous vegetation and sometimes roads. Meadows and fields with scattered groups of shrubs near breeding habitat seem particularly attractive to feeding adults. Depending on weather conditions, the flight season extends from late May to early October in Illinois and from early July through August in Wisconsin. Adults may live from 5 to 6 weeks.
Predation. Potentially, there are many natural enemies of dragonflies during all stages of the life history. Early instars may be eaten by larger predatory insects, fish, and turtles in their aquatic habitat. Mature larvae are vulnerable to predation by birds and frogs when they crawl out of the water to emerge. The newly emerged adults are particularly susceptible to predation, because they are still soft and are not able to fly well. During periods of drought, adults and larvae may become more concentrated near the remaining water where predators such as birds and frogs may be lurking. Spiders, especially the orb-weavers, occasionally trap Hine's emerald dragonflies in their webs.
Habitat destruction or alteration. In Illinois, populations of Hine's emerald dragonfly seem to be rare and localized. Much of the known remaining habitat has been reduced due to industrialization and urbanization. Pressures of urbanization also have contributed to development of additional roads, bridges, and golf courses. Contamination of surface and ground water from industrial sites, as well as petroleum products and road salt could be a major threat to the larval habitat.
In Door Co., Wisconsin, populations of Hine's emerald dragonfly appear to be larger, and breeding habitat seems more extensive. Development of the land by agricultural and tourist/recreational industries is of concern here. Pesticide use at apple and cherry orchards is a potential threat. Non-point runoff and groundwater to surface water recharge are possible vehicles for water quality contamination by pesticides.
Continuing research. Studies continue to be conducted on Hine's emerald dragonfly population levels in Illinois and Wisconsin. More detailed knowledge of the life history, micro habitat of the larva, food habits, and genetics will be of importance in conserving this species. An understanding of the genetics of this species is important for discerning the relationships of widely separated populations and re-establishing populations at historic sites. Surveys will continue to be conducted for Hine's emerald dragonfly in other areas suspected to have suitable breeding habitat. For more information please see the recovery plan, available in PDF format.
Acknowledgments. This research was supported primarily by funds from Material Service Corporation with additional funds provided from the U.S. Fish and Wildlife Service, the Illinois Department of Natural Resources, the Illinois Department of Transportation, and the Wisconsin Department of Natural Resources. Cooperative field studies were conducted by Illinois State Museum, TAMS Consultants, Inc., and the Illinois Natural History Survey.
Comments or questions? Please mail them to Dr. Everett D. (Tim) Cashatt, Curator of Zoology