Anax junius
From ize2010
The Green Darner
| Common Green Darner | |
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| photo by Joyce Gross | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Insecta |
| Order: | Odonata |
| Suborder: | Anisoptera |
| Family: | Aeshnidae |
| Genus: | Anax |
| Species: | A. junius |
| Binomial name | |
| Anax junius Drury, 1973 |
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Contents |
Morphology
Fully grown adults are usually about 7.6cm long and have a wingspan of 11.4 cm. In both sexes wings are clear with yellow edges around the veins. Males have a bright green thorax and a blue abdomen which can become purple when the darner is cool. The abdomen displays a dark dorsal stripe that broadens at one end. The face of males displays a blue semicircle “bulls-eye” pattern on its forhead, with the rest of his face being pale green. Females have a green thorax as well, but often grayish-green on the sides. A Females thorax is green, but often grayish-green on the sides. The abdomen can be rusty brown to purple, and displays a dark dorsal stripe. (1), (2), (3)
Life Span
Nymphs (aquatic larval stages) lasts for 2-3 years. Green Darners only live 4-7 weeks after adult emergence. (2)
Development
Eggs are laid at one time in aquatic vegetation, beneath the waters surface and hatch in the springtime. Green Darner nymphs pass through 11-12 larval stages before metamorphosing into adult dragonflies. Mature nymphs will crawl up emergent plants before emerging as an adult. After emergence from the final nymph casing, the dragonfly must rest and dry its wings in order for them to harden before flight can take place. In only a few weeks the adult dragonfly will reach sexual maturity. (1), (3)
Reproduction
as Common green darners reach sexual maturity, they begin seeking out fresh water ponds to find a mate. Male dragonflies have claspers at the end of their abdomen, but no external genitalia. Before mating occurs, a male transfers sperm from his sperm producing genitals (located in segment 9 at the tip of his abdomen)and attaches the spermatophore to his second abdominal segment, and then grabs a female around the neck with his claspers. The female then receives the spermatophore through the genital opening of her abdomen. Dragonflies mate during flight, and the male will fly in tandem with the female in order to guard her from possible sexual assaults by other males. (1), (2), (3), (5)
Distribution
Widespread throughout North America. They are found in every state and in southern Canada. (1)
Habitat
green darners live in a wide variety of wetlands, including permanent and temporary ponds and lakes. (1)
Predation and Prey
Adult dragonflies and immature nymphs are very predacious. Nymphs feed on tadpoles, small fish, and aquatic insects. Dragonfly nymphs have acquired a unique modification to their labium allowing it to be extended rapidly toward potential prey. Hooked lobes at the tip of the labium grasp the prey and brings it back to the mouth as the labium retracts. For this reason nymphs can be very aggressive hunters and often leave themselves exposed and fall prey to predatory fish. This modification of the labium has been acquired by all Odonata nymphs. Adult dragonflies will eat any soft-bodied insects including mosquitoes, flies, butterflies and moths. (1), (2), (3), (4), (5)
References
(1) "Anax Junius | USA National Phenology Network." USA National Phenology Network | USA National Phenology Network. Web. 12 May 2010. <http://www.usanpn.org/Anax_junius>.
(2) "Common Green Darner (Anax Junius)." Texas Parks & Wildlife Department | Welcome. Web. 12 May 2010. <http://www.tpwd.state.tx.us/huntwild/wild/species/greendarner/>.
(3) Meyer, John. "Odonata." Web. 12 May 2010. <http://www.cals.ncsu.edu/course/ent425/compendium/odonata.html>.
(4) Tony-2, John Balaban, and Jane Balaban. "Species Anax Junius - Common Green Darner - BugGuide.Net." Welcome to BugGuide.Net! - BugGuide.Net. Web. 12 May 2010. <http://bugguide.net/node/view/585>.
(5) United States. U.S. Department of Agriculture. Extension.oregonstate.edu/catalog/pdf/ec/ec1601.pdf. By M. Grunberg and N. Allen. Oregon State University, 2007. Web. 11 May 2010.
