Common green darner  (Anax junius)

The common green darner is classified as Least Concern (LC) on the IUCN Red List (1).

One of North America’s most common and widespread dragonflies (6) (7), the common green darner (Anax junius) is a large insect with a bright green head and thorax and a contrasting blue abdomen. In the female and immature common green darner, the abdomen is dull green, reddish or brown, and in all individuals there is a black line running down its upper surface (2) (3) (4) (5) (6). The name ‘darner’ is thought to derive from the long, narrow abdomen typical of dragonflies in the Aeshnidae family, which somewhat resembles the shape of a darning needle (7).

The common green darner has a yellowish-green face and large, dark green eyes, which meet on the top of the head. Both the male and female have a distinctive “bull’s-eye” mark on the top of the forehead, consisting of a black or brown spot ringed with blue and yellow (2) (3) (4) (6) (7). The wings of the common green darner are clear, but become tinged amber with age, particularly in females (2) (3) (4) (5) (6). The legs are brown to black (2).

This species can sometimes be mistaken for the giant darner (Anax walsinghami), but the latter has a much longer abdomen (6). The female common green darner is distinguished from the comet darner (Anax longipes), another reddish-brown dragonfly, mainly by the bull’s-eye mark on the forehead (3) (6). Like other Anax species, the common green darner may turn greyish to dark purple when cold (8) (9), possibly allowing it to absorb more heat from the sun (8).

The common green darner is widespread across North America, occurring in Alaska and southern Canada, throughout the United States, and south to Mexico, as well as sometimes further south in Central America. It is also found on Bermuda and in the Caribbean, including Cuba, the Bahamas, the Cayman Islands, the Dominican Republic, Haiti, Jamaica, Puerto Rico and the British Virgin Islands (1) (2) (4) (6).

This species has also occasionally been recorded outside of its normal range, in Hawaii, northeast Asia, the United Kingdom and France (2) (4) (6).

A migratory species, the common green darner can be found in a wide range of habitats during migration, both close to and away from water (1) (4) (6). However, breeding normally takes place in a variety of stillwater habitats, including ponds, lakes, marshes, swamps, slow-moving streams and estuaries (1) (3) (4) (5) (6).

The common green darner has an unusual breeding strategy, being one of very few dragonflies to migrate in spring and autumn. Some individuals behave like other dragonflies, overwintering as larvae before emerging as adults in the spring. However, large proportions of the population move south in the autumn, often flying in large swarms, and are believed to breed during the winter in Mexico, the Caribbean and the far south of the United States. There, the larvae develop over winter, and it appears to be the new generation of adults that travels north again in spring to breed in northern areas over the summer. The offspring produced in the summer then undertake the next southward migration as immature adults (1) (4) (6).

Like other dragonflies, the common green darner is an agile and opportunistic predator, with excellent vision (8) (10). Adults of this species feed during the day or at dusk, often foraging in swarms over rivers, lakes or fields when prey is abundant (3) (4) (6). The diet consists of a variety of flying insects, including butterflies and even other dragonflies (5) (6). The larvae of the common green darner are also opportunistic predators, taking a variety of aquatic invertebrate prey, as well as fish eggs and tadpoles (5) (11) (12). Prey is caught by the larva shooting out its lower jaw, or ‘labium’, which is armed with hooks that impale the victim (8) (10).

Adult male common green darners patrol stretches of water, chasing intruders and pursuing potential mates (4) (5). After mating, the female lays the eggs in aquatic vegetation (4) (5) (6). Uniquely among North American darners, the male and female common green darner often fly in tandem pairs while the female is laying the eggs, although rival males will often try to break up these pairs in an attempt to mate with the female (4) (6).

The larva of the common green darner is long and smooth and usually marked with green and brown (13). Dragonfly larvae, also known as nymphs, are aquatic and pass through a number of developmental stages, often over a relatively long period, before emerging from the water and moulting into the adult form. The newly emerged adult then spends some time feeding and maturing before it is ready to breed (5) (8) (10).

The common green darner is a widespread and abundant species, and is not known to face any major threats (1). It is possible that, like other dragonflies, the common green darner is at risk in some areas from pollution and from the destruction and degradation of wetland habitats (8) (10), but it is not currently considered to be globally threatened (1).

There are no specific conservation measures known to be targeted at the common green darner. This species occurs in many protected areas throughout its range, but its migratory behaviour means that cross-border cooperation may be needed if this large dragonfly ever requires conservation attention in the future (1).

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

Find out more about the common green darner:

• Texas Parks and Wildlife Department - Common Green Darner (Anax junius):
  http://www.tpwd.state.tx.us/huntwild/wild/species/greendarner/

More information on dragonfly and damselfly conservation:

• Moore, N.W. (1997) Dragonflies: Status Survey and Conservation Action Plan. IUCN/SSC Odonata Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
  http://data.iucn.org/dbtw-wpd/edocs/1997-042.pdf