Edmund's snaketail (Ophiogomphus edmundo)

Description

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Edmund's snaketail fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Edmund's snaketail description

Edmund’s snaketail (Ophiogomphus edmundo) is a beautifully patterned, slender dragonfly, distinctly striped with brown on the thorax. The body is greenish, and the abdomen is smooth and blackish, becoming paler and hairy on the underside. Edmund’s snaketail has a well-defined brown stripe running lengthways down the centre of the thorax, separated in the middle by a yellow ridge. A broad yellowish stripe covers the first two segments of the abdomen and narrows to a line on the third segment. A broad, broken stripe is visible on the rest of the abdomen, except for the ninth segment which has a round spot. The last segment of the abdomen is mostly yellow ⁽²⁾.

This species has a pale greenish to yellowish-green face, with a narrow line of pale cinnamon-brown on the upper lip of the mouthparts. The top of the head is black, and Edmund’s snaketail has a pair of black antennae which have a narrow ring of white around the stout base. The back of the head is yellowish and fringed with a crest of long, blackish hairs. Edmund’s snaketail has pale lower legs, which turn darker towards the knees and black on the upper parts of leg ⁽²⁾.

The female Edmund’s dragonfly is very similar to the male, but the wide central stripe on the thorax is less clearly divided by the yellow ridge. The female also has a very small pair of black horns on the sides of the head which appear blunt and crumpled ⁽²⁾. 

Also known as

Edmund.

Size

Length: 4.5 - 4.8 cm ⁽²⁾

Edmund's snaketail biology

Very little specific information is available about the biology of Edmund’s snaketail, although it is presumed to spend much of its time among trees and patches of vegetation. The larvae of this species have been recorded in highly oxygenated riffles ⁽³⁾.

Dragonfly larvae are highly mobile aquatic predators, feeding on a wide variety of aquatic prey, including minute crustaceans and other invertebrates. The larvae stalk their prey, locating it mainly by sight. Once it is close enough, they catch their prey by shooting out their lower jaw, using pressure that has built up in the muscles ^{(7) (8)}. The lower jaw, called the labium, has hinged hooks which grasp the prey and drag it back to the mouth as the jaw retracts ⁽⁷⁾.   

The length of the larval stage varies between species, although it may range from a few weeks to several years. During this time, the larvae undergo a series of moults, passing through several developmental stages known as instars or stadia ^{(7) (8)}. Shortly before the final moult, the dragonfly larvae stop feeding and move to sites where they can emerge, usually in vegetation. The larvae emerge from their final moult having metamorphosed into adult dragonflies, with characteristic features such as wings and enlarged compound eyes ⁽⁷⁾. The wings of the newly emerged adult rapidly expand and harden, with the first flight occurring soon after the final moult ^{(7) (8)}. The new dragonflies then leave the water, spending anything from a few days to several weeks feeding and maturing ⁽⁷⁾.

Adult dragonflies are agile, opportunistic predators with exceptional eyesight, preying on a wide variety of flying insects. Following the maturation period, adult male dragonflies return to the water, with many species setting up territories which are aggressively defended against other males. Female dragonflies typically only return to water to mate ^{(7) (8)}.

Mating dragonflies adopt a characteristic ‘wheel’ position, with the male grasping the female by the head using claspers on the end of the abdomen, while the female bends the tip of her abdomen forward to reach the male genitalia on the second and third segments of the male’s abdomen ^{(7) (8)}. The female typically lays eggs almost immediately after mating, and is often guarded by the male ⁽⁷⁾.

Edmund's snaketail range

Occurring in just three states in the United States, Edmund’s snaketail has a relatively restricted distribution. It is known only from the Conasauga River in Tennessee and Georgia, from two locations in the Catawba drainage in North Carolina, and from a tributary of the Chattahoochee River in north Georgia ^{(1) (3) (4) (5)}.  

Edmund's snaketail habitat

Edmund’s snaketail typically inhabits clear, moderately flowing mountain streams ^{(1) (3) (5)}, with a sand or gravel substrate ^{(4) (6)}. The adults often fly over shallow riffles or perch on rocks ^{(3) (4)}. 

Away from water, Edmund’s snaketail perches on the ground or in vegetation, including bushes, branches, or tree canopies, in open woods ⁽⁶⁾.

Edmund's snaketail status

Edmund’s snaketail is classified as Endangered (EN) on the IUCN Red List ⁽¹⁾.

Edmund's snaketail threats

Edmund’s snaketail is threatened by the impounding and channelling of water to develop dams and reservoirs for hydroelectric schemes, irrigation and water supplies. Siltation, drainage and pollution also pose further threats to this species as they destroy freshwater habitats by lowering the water table, sometimes turning permanent waterbodies into temporary water sources ^{(1) (3) (8)}.

Pollution from sewerage and industrial waste, fertiliser run-off and pesticide drift have wiped out or greatly reduced the populations of many species of dragonfly, and is likely to similarly affect the population of Edmund’s snaketail ⁽⁸⁾.

Edmund's snaketail conservation

The Conasauga River runs through fairly rugged, inaccessible country in national forests in Tennessee and Georgia, which affords some level of protection to Edmund’s snaketail in these areas. It is also state-listed in Georgia ⁽¹⁾.

The IUCN/SSC Odonata Specialist Group has identified key priorities for dragonfly conservation as establishing Protected Areas, such as National Parks and nature reserves, as well as ensuring that activities in existing protected areas are managed appropriately. Additionally, the IUCN/SSC Odonata Specialist Group recognises the need to conserve habitats outside Protected Areas by modifying agricultural, forestry and industrial practices ⁽⁸⁾.

To effectively conserve dragonfly populations, the IUCN/SSC Odonata Specialist Group has outlined a number of measures, including research into the taxonomy, distributions and biological requirements of dragonfly species, and controlling pollution at key dragonfly sites. It also recommends amending legislation to provide protected areas and control development and pollution, as well as carrying out educational campaigns to raise public awareness ⁽⁸⁾.

Find out more

Find out more about dragonfly conservation:

• Moore, N.W. (Ed.) (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

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Glossary

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).

Antennae

Pair of sensory structures on the head of invertebrates.

Crustaceans

Diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones), echinoderms, and others.

Larvae

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.

Moults

In insects, referring to stages of growth, whereby the hard outer layer of the body (the exoskeleton) is shed and the body becomes larger.

Riffles

Light rapids where water flows across a shallow section of river.

Taxonomy

The science of classifying organisms, grouping together animals which share common features and are thought to have a common ancestor.

Territory

An area occupied and defended by an animal, a pair of animals or a colony.

Thorax

Part of the body located near the head 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.

References

1. IUCN Red List (May, 2011)
   http://www.iucnredlist.org/
2. 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, Los Angeles.
3. Bick, G.H. (2003) At-risk Odonata of conterminous United States. Bulletin of American Odonatology, 7(3): 41-56.
4. USDA Forest Service. (2002) Wildlife Food Plot Renovation: Biological Evaluation on Georgia DNR Wildlife Management Areas, Brasstown, Toccoa, Chattooga, and Tallulah Ranger Districts, Chattahoochee National Forest. USDA Forest Service, Washington D.C. Available at:
   http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsm9_028931.pdf
5. Georgia Department of Natural Resources, Wild Resources Division.  (2005) A Comprehensive Wildlife Conservation Strategy for Georgia. Georgia Department of Natural Resources, Wild Resources Division, Georgia. Available at:
   http://www1.gadnr.org/cwcs/Documents/strategy.html
6. 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. John Hopkins University Press, Baltimore, Maryland.  
7. O'Toole, C. (2002) The New Encyclopedia of Insects and their Allies. Oxford University Press, Oxford.
8. Moore, N.W. (Ed.) (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