Dragonhunter (Hagenius brevistylus)

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⁾.
 

Also known as

black clubtail, dragon hunter.

Size

Length: 7 - 9 cm ⁽²⁾
 

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 found throughout North America, occurring in 5 provinces in Canada and 34 states in the United States ⁽¹⁾.

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:

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

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

Abdomen

In arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree (but not visibly in most spiders). In crustacea (such as crabs), some of the limbs attach to the abdomen; in insects the limbs are attached to the thorax (the part of the body nearest to the head) and not the abdomen.

Detritus

Litter formed from fragments of dead material.

Exoskeleton

An external skeleton that supports and protects an animal’s body.

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Larvae

The stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Metamorphosis

An abrupt physical change from the larval to the adult form.

Nymph

Stage of insect development, similar in appearance to the adult but sexually immature and without wings. The adult form is reached via a series of moults, and the wings develop externally as the nymph grows.

Territorial

Describes an animal, a pair of animals or a colony that occupies and defends an area.

Thorax

Part of the body located between the head and the abdomen in animals. In insects, the three segments between the head and the abdomen, each of which has a pair of legs. In vertebrates the thorax contains the heart and the lungs.

1. IUCN Red List (June, 2012)
   http://www.iucnredlist.org/
2. Garrison, R.W., von Ellenrieder, N. and Louton, J.A. (2006) Dragonfly Genera of the New World: An Illustrated and Annotated Key to the Anisoptera. The Johns Hopkins University Press, Baltimore and London.
3. Eaton, E.R., Kaufman, K. and Bowers, R. (2007) Field Guide to Insects of North America. Houghton Mifflin Harcourt, Boston, Massachusetts.
4. Dunkle, S.W. (2000) Dragonflies Through Binoculars: A Field Guide to Dragonflies of North America (Butterflies Through Binoculars Series). Oxford University Press, Inc., New York.
5. Needham, J,G. (1981) A Manual of the Dragonflies of North America (Anisoptera : Including the Greater Antilles and the Provinces of the Mexican Border). University of California Press, Berkeley and Los Angeles.
6. Capinera, J.L. (2008) Encyclopedia of Entomology. Springer, Berlin.
7. Paulson, D. (2009) Dragonflies and Damselflies of the West. Princeton University Press, Princeton, New Jersey.
8. Dunn, G.A. (1996) Insects of the Great Lakes Region. The University of Michigan Press, Ann Arbor, Michigan.
9. Marshall, S.A. (2007) Insects: Their Natural History and Diversity: A Photographic Guide to Insects of Eastern North America. Firefly Books Ltd., Ontario, Canada.
10. Johnson, C. (1972) Tandem linkage, sperm translocation, and copulation in the dragonfly, Hagenius brevistylus (Odonata: Gomphidae). American Midland Naturalist, 88(1): 131-149.
11. Berger, C. (2004) Dragonflies: Wild Guide. Stackpole Books, Mechanicsburg, Pennsylvania.
12. Ackerman, J. (2006) Dragonflies strange love. National Geographic Magazine, April. Available at:
    http://ngm.nationalgeographic.com/print/2006/04/dragonfly-mating/ackerman-text
13. Moore, N.W. (1997) Dragonflies - Status Survey and Conservation Action Plan. IUCN/SSC Odonata Specialist Group, IUCN, Gland, Switzerland and Cambridge. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/1997-042.pdf