
Friday 25 January
Kingdom | Animalia |
Phylum | Arthropoda |
Class | Insecta |
Order | Odonata |
Family | Gomphidae |
Genus | Hagenius (1) |
The largest of the North American clubtail dragonflies (Gomphidae family), the invertebrates_freshwater (Hagenius brevistylus) is an aptly named species, specialised in feeding on dragonflies and other large insects (3). The only member in its genus (4), the dragonhunter is a large and distinctive dragonfly, with long, powerful legs and wings (4) (5). Like other clubtails, the dragonhunter has a distinctly enlarged end to its abdomen, commonly known as the ‘club’, which is usually significantly larger in the male than in the female (5) (6).
Clubtail dragonflies are often beautifully camouflaged, usually being brown or black and marked with yellow or green (6). The invertebrates_freshwater is no exception, being primarily black on the body, with two wide yellow stripes on the thorax and yellow markings on the abdomen (4) (5) (7) (8). The yellow markings on each side of the abdomen appear as a mixture of stripes, small triangles and spots (7). This species has a yellow face with a fine black line running across it, and large green eyes (5) (7) which are widely spaced on top of the head (3) (6). The legs are black (4) (5) (7).
Aside from the enlarged club at the end of the male’s abdomen, the male and female dragonhunter are generally similar in appearance, although the yellow patterning on the abdomen is usually much more visible in the female. The abdomen of the male dragonhunter also appears somewhat more compressed than that of the female, and is distinctive during flight, often being bent downward in a characteristic ‘J’ shape (5).
An easily recognisable species, the dragonhunter is most commonly seen throughout the spring and summer months, from mid-April to mid-September, depending on the location. Away from water, the dragonhunter appears a somewhat wary species, often lurking in cover close to the ground, in trees, or along the forest edge (5). The adults of this species commonly perch horizontally on the ground, on stones, logs, or on the branches of trees and shrubs (6) (7).
As its common name suggests, the invertebrates_freshwater is a voracious predator, feeding on other dragonflies, as well as butterflies and other large insects (2) (4) (5) (7). When hunting for prey, the dragonhunter will perch motionless and wait for insects to pass by, or will fly up and down along the water’s edge, actively searching for prey on which to feed (7). The dragonhunter is frequently observed foraging along open roads or swooping through sunny openings, close to woods and streams (4).
The male invertebrates_freshwater is likely to be territorial during the breeding season (10). Once the male has attracted a female, the pair will engage in the characteristic tandem mating position of dragonflies in which the male grasps the female using claspers at the tip of the abdomen (11). The male dragonhunter has the dubious distinction of inflicting more damage to the female during mating than any other dragonfly, sometimes gouging the female’s eyes, piercing the exoskeleton, or puncturing holes in the female’s head (5) (12).
Immediately after mating, the female will fly close to the surface of the water to lay the eggs, swooping down rhythmically to tap the water’s surface with the tip of the abdomen. The female may sometimes lay the eggs while hovering, dropping to the water to tap the surface before rising up again, or at other times may make long egg-laying flights over open water (2) (4) (5) (7).
The larvae, or nymphs, of the dragonhunter are exceptionally long-lived, remaining in the water for four or more years before metamorphosing into adults (9).
The dragonhunter is able to use many different habitats, and is found in a wide variety of streams, rivers and lakes (1) (7). It is particularly common around forested streams and rivers with a moderate to fast current (5).
The larva of the dragonhunter does not burrow like that of many other dragonfly species, and instead rests among leaf litter and detritus in the quiet margins of lakes and streams (1) (2) (6) (9).
The dragonhunter is classified as Least Concern (LC) on the IUCN Red List (1).
This species is not currently known to be facing any specific threats.
However, dragonflies in general are heavily affected by pollution, particularly from sewage and industrial wastes, fertiliser run-off and pesticide use (13). Clubtails, such as the invertebrates_freshwater, breed in flowing water and are therefore considered to be very susceptible to pollution, especially due to their long life cycles (5).
The damming of rivers for hydroelectric schemes and water supplies can have a detrimental impact on dragonfly populations, while drainage and excessive water extraction can also negatively affect freshwater habitats and the species that depend on them (13).
There are no known conservation measures currently targeted at the invertebrates_freshwater. However, this species occurs in many federal, state, local and private reserves, which may afford it some level of protection (1).
Find out more about dragonfly conservation:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk
Image credit
© Elaine J. Miller
Elaine J. Miller
ejmphoto01@gmail.com
http://www.flickr.com/photos/27695964@N03/
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This species is featured in:
This species is featured in the Wisconsin's Northwoods eco-region