Animal Diversity Web

Geographic Range

The breeding range of Anax junius extends from the northernmost part of the United States (Alaska) and south to Panama; also occurs from Hawaii east to Nova Scotia; also occurs in West Indies and Tahiti. Known to occur in Asia from Kamchatka south to Japan and mainland China (Cannings et. al., 1991).

Habitat

The Green Darner prefers still or very slow-moving fresh water, with lots of aquatic vegetation, and can only flourish where there are no predatory fish.

• Aquatic Biomes
• lakes and ponds
• rivers and streams

Physical Description

The Green Darner is one of the largest dragonflies, with male sizes ranging from 70-76 millimeters in length and 90-104 millimeters in expanse, and female sizes ranging from about 68-80 millimeters in length and 90-106 millimeters in expanse. Both male and female are characterized by green thoracic region and a reddish-brown coloration ventrally in the abdominal region, with the female having slightly lighter coloration. Both male and female members of this species show light blue abdominal coloration dorsally. Nymphs are fully aquatic, six-legged, with large lateral eyes, elongate wingpads, and underslung mouthparts. Maximum length of nymphs 50-55mm (Jaques 1947, Needham 1927, Bright and O'Brien 1998 ).

• Other Physical Features
• ectothermic
• bilateral symmetry

Reproduction

Reproduction usually occurs in the summer months of July and August. Due to the briefness of the adult darner's life cycle (perhaps only a few weeks), they are mainly concerned with reproduction. To prepare for copulation, the male loops his abdomen forward to transfer semen from his true genital opening to a receptacle located in his secondary genitilia. Now the male is ready to select a mate. Once he has done so, the male will fly up to the female and, using his genital claspers located at the tip of his abdomen, he will grab hold of her by the neck to ensure that she will not escape. The two will form what looks like a circle with their bodies as the female aligns her genitilia with the secondary genitilia of the male located at the base of his abdomen. The male will then insert his secondary sex organ into the female's vagina, packing down or removing the sperm of any previous mates. Only after this will the male deposit his own sperm into the female.

After copulation, the male will continue to hold onto the female's neck, probably for the rest of the day, in order to prevent any other males from mating with her, removing his sperm, and replacing it with their own. The male will fly around with the female while she lays her eggs, often guiding her to the most ideal spot for the eggs. Once a location has been selected, the female will insert her ovipositor, a knife-like egg-laying organ, into pieces of rotting wood or in the stems of growing plants at the edge of a pond. This egg-laying procedure is the only form of nurturing that the offspring will receive from their mother. Females always lay copious amounts of eggs in order to ensure that at least some will hatch and fully mature into adult dragonflies (Waldbauer, 1998; Needham, 1929).

Green Darner eggs will hatch within about three weeks and small spider-like nymphs will emerge.

In warm water regions, where food is plentiful, a nymph may develop in as little as one summer, but as more often is the case, in cold water regions, where food is less plentiful, a nymph may take as long as four years to fully develop into an adult darner (Cannings et. al., 1991). Some adults migrate south in winter, and return north to lay eggs the following spring (Bright and O'Brien 1998).

Behavior

Since males must select a territory that is attractive to females and defend it from other would-be mates, males are often observed to hold races over the ponds and duel in spectacular aerial battles for the rights to mate with the females darners in that territory (Cannings et. al., 1991).

Food Habits

Green Darner nymphs are wholly carnivorous, usually eating aquatic insects, tadpoles, and very small fish. Adult Darners catch and eat insects on the wing, including moths and mosquitos. Dragonflies are excellent aerial hunters, due to its tremendous flying speed (recorded at up to 18 mph) and incredible eyesight. They use their powerful jaws to tear apart and chew up their prey (Wootton, 1984; Jaques, 1947).

Economic Importance for Humans

Economic Importance for Humans: Positive

Green Darners feed on many insects that are harmful to humans and the environment, especially mosquitoes.

Economic Importance for Humans: Negative

Green Darners sometimes feed on beneficial insects like honeybees.

Conservation Status

This species is fairly common and abundant throughout its range. The main threat to its persistence is destruction of the freshwater habitat it requires to breed.

• IUCN Red List

  Least Concern
  More information

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Contributors

Paul Roach (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

References

Bright, E., M. O'Brien. 1998. "Odonata Larvae of Michigan: Keys for, and notes on, the dragon- and damselfly larvae found in the State of Michigan" (On-line). Accessed 5 March 2001 at http://insects.ummz.lsa.umich.edu/michodo/test/index.htm.

Cannings, S., R. Cannings, R. Cannings. 1991. Distribution of the Dragonflies (Insecta: Odonata) of the Yukon Territory, Canada, with notes on ecology and behavior. Contributions to Natural Science No. 13.. Victoria, B.C., Canada: Royal British Columbia Museum.

Jaques, H. 1947. How to Know the Insects. Dubuque, Iowa, USA: William C. Company.

Needham, J. 1929. A Handbook of the Dragonflies of North America. Springfield, Ilinois, USA: Charles C. Thomas.

Waldbauer, G. 1996. Insects of the Seasons. Cambridge, Massachusetts, USA: Harvard University Press.

Waldbauer, G. 1998. The Birder's Bug Book. Cambridge, Mass.: Harvard University Press.

Wootton, A. 1984. Insects of the World. New York, N.Y.: Facts on File Publications.