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.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Green Darners sometimes feed on beneficial insects like honeybees.
Green Darners feed on many insects that are harmful to humans and the environment, especially mosquitoes.
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).
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).
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
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 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).
The green darner or common green darner[3] (Anax junius), after its resemblance to a darning needle, is a species of dragonfly in the family Aeshnidae. One of the most common and abundant species throughout North America, it also ranges south to Panama.[4] It is well known for its great migration distance from the northern United States south into Texas and Mexico.[5][6] It also occurs in the Caribbean, Tahiti, and Asia from Japan to mainland China.[7] It is the official insect for the state of Washington in the United States.
The green darner is one of the largest extant dragonflies; males grow to 76 mm (3.0 in) in length with a wingspan up to 80 mm (3.1 in).[7][8]
Females oviposit in aquatic vegetation, eggs laid beneath the water surface. Nymphs (naiads) are aquatic carnivores, feeding on insects, tadpoles, and small fish. Adult darners catch insects on the wing, including ant alates, moths, mosquitoes, and flies.
Dru Drury described this species as Libellula junius in 1773.[9] There are not currently any recognized subspecies. There are three recognized synonyms: Anax spiniferus Rambur, 1842; Anax ocellatus Hagen, 1867; Anax severus Hagen, 1867.
Common Green Darners are commonly found throughout the continental United States and southern Canada, occasionally ranging as far south as Panama, particularly in the winter.[10] There are also populations in Hawaii and the Caribbean. Vagrant individuals have been seen far outside of their normal range including sightings in Alaska, Russia, China, Japan, France, the United Kingdom, India, and Bermuda. These vagrant sightings are likely migrating individuals blown off-course by strong winds or storms.[11]
Common Green Darners are large dragonflies, ranging from 6.8 to 8 cm (2.7 – 3.1 inches)[12] in length and a wingspan of up to 10 cm (3.9 inches).[13] Both sexes have an unmarked green thorax. Mature males have bluish-purple abdomens (the first few abdominal segments are the brightest) with a black dorsal stripe that broadens near the end of the abdomen. Immature males and most females have reddish-brown abdomens, but some females are patterned like adult males. Wings are initially clear but usually become amber-tinted with age, especially in females.[13][14] Both sexes have a black ‘bulls-eye’ mark on the face (more precisely, the frons) in front of their eyes, a distinguishing field mark that separates them from the superficially similar Comet Darner (Anax longipes).[15][13] This species oviposits in tandem which is a unique behavior among North American darners.[15][13]
Both the adult and the nymphal stage are predators. Nymphs prey upon immature aquatic insects (including conspecifics), small crustaceans, small tadpoles, and even small fish. Adults primarily prey on winged insects, including wasps, flies, butterflies, and other Odonates. The primary predators of Common Green Darner nymphs are fish. Adults are preyed upon by birds and occasionally robber flies, spiders, and other large dragonflies.[16]
Nymphs develop in lakes, ponds, and slow streams and rivers.[17] Adults are most frequently seen around nymph habitat but they are strong fliers and can be found in a wide variety of habitats including grasslands, forests, and urban areas.[18]
There are several species of migratory dragonflies in North America, but Common Green Darners are the best studied.[19] Other migratory species include
The large geographic range and migratory behavior of the Common Green Darner has made it a challenge to piece together its complex life history. Recent research has indicated that the annual life cycle of Anax junius is likely composed of at least three different generations.[20] The first generation emerges in the southern end of its range in early spring and migrates northwards through spring and summer. The second generation emerges in the northern end of its range in summer and migrates southwards in fall. The third generation occurs in the south during the winter and does not migrate. Common Green Darners migrate in fall and spring but for several reasons the southward movement in fall is more noticeable[21].
By attaching micro-radio transmitters to Common Green Darners, researchers have found them to be capable of migrating up to 140 kilometers in a day, though they typically cover less distance per day. A group of researchers used stable isotope analysis on individuals collected between Ontario and Mexico during fall and documented that>90% of individuals moved southward, with an average distance of 900 kilometers.[22]
A study published in 2019 attached miniaturized radio transmitters to Common Green Darners in the Great Lakes region and tracked their movement with the Motus Wildlife Tracking System. Individuals moved at an average groundspeed of 16 km/hour.[23]
Mating, wheel position
Egg-laying
Female
Uncommon blue form female, Ottawa, Canada
Hovering San Joaquin Wildlife Sanctuary
The green darner or common green darner (Anax junius), after its resemblance to a darning needle, is a species of dragonfly in the family Aeshnidae. One of the most common and abundant species throughout North America, it also ranges south to Panama. It is well known for its great migration distance from the northern United States south into Texas and Mexico. It also occurs in the Caribbean, Tahiti, and Asia from Japan to mainland China. It is the official insect for the state of Washington in the United States.
The green darner is one of the largest extant dragonflies; males grow to 76 mm (3.0 in) in length with a wingspan up to 80 mm (3.1 in).
Females oviposit in aquatic vegetation, eggs laid beneath the water surface. Nymphs (naiads) are aquatic carnivores, feeding on insects, tadpoles, and small fish. Adult darners catch insects on the wing, including ant alates, moths, mosquitoes, and flies.
