Scientific Name: Ophiogomphus howei
Taxonomy Group: Arthropods
Range: Ontario, New Brunswick
Last COSEWIC Assessment: November 2008
Last COSEWIC Designation: Special Concern
SARA Status: Schedule 1, Special Concern
Image of Pygmy Snaketail
The Pygmy Snaketail is a small dragonfly, 31 to 37 mm in length. It is the smallest of the snaketails and one of the smaller dragonflies in North America. As with all snaketails, the Pygmy Snaketail is dark brown and black, with vivid yellow markings on the dorsal abdomen and bright green on the thorax. In this species, the wings of both sexes are marked basally with a large, transparent yellow-orange field or patch. This distinguishes it from almost all other North American dragonflies. The female resembles the male except for its thicker abdomen and reduced flare, among other things. The larvae are small and cryptic. They can be distinguished from the young larvae of other species by the absence of dorsal abdominal hooks, although small bumps are present.
Distribution and Population
The Pygmy Snaketail occurs only in eastern North America. It has been found along the Appalachian Mountains from northern New Brunswick to southeastern Tennessee, as well as in a disjunct centre of distribution that includes Michigan, Minnesota, Wisconsin and northwestern Ontario. In Canada, there are 12 known sites: 11 in New Brunswick and 1 in Ontario. The Pygmy Snaketail was first reported in Canada in 2002 on the banks of the Saint John River in northern New Brunswick. The sites near the United States border are on the St. Croix River in southwestern New Brunswick. It also occurs on the Magaguadavic, Miramichi and Salmon rivers. Captures of only 102 individuals of the Pygmy Snaketail have been confirmed in Canada (101 in New Brunswick and 1 in Ontario). Population size is unknown, but several hundred individuals are likely necessary to ensure survival of the species. The data in hand are insufficient to assess long-term population trends. Given the relatively good condition of the Saint John River at Baker Brook where the Pygmy Snaketail was encountered, and the lack of recent heavy impact on rivers in the region, it is likely but unproven that the Canadian population is stable at its current level.
Habitat requirements in dragonflies are largely those of the larvae. Prior to ovipositing (egg laying), the adults are believed to spend the bulk of their time in surrounding forests. The Pygmy Snaketail is a species that occurs in large, clear, fast-flowing, clean rivers that have moderate slopes and pea gravel or sandy bottoms. The species has been observed laying eggs in smooth-flowing reaches of otherwise tumultuous rivers, and the larval skins from which the adults emerge are commonly found on the erosional banks near where the current is strong. These observations suggest that the larvae either live in areas near these banks where the current is strong, or drift there prior to emerging close to the water’s edge. Prior to emergence, the larvae are thought to live on or burrowed deep within the sand or gravel substrate. Generally speaking, searches for larval skins at many seemingly appropriate waters, and at the appropriate time of the year, have yielded no results for the species. This suggests that the species seeks specific conditions that have yet to be precisely defined.
As with many dragonflies, the eggs of Pygmy Snaketails are laid into water, rather than into plants, by dipping the end of the abdomen to release them. These eggs are carried by the current and eventually sink to the bottom, downstream from the ovipositing site. During the day, the Pygmy Snaketail larvae burrow to a depth of up to 20 cm in the soil. At night, they come to the surface and drift with the current. The exact length of time required for the larvae to develop to emergence is unknown; however, it is believed to take at least two years. The adults generally emerge close to the water’s edge, at the same time as the adults of other snaketails. In 2002, emergence on the Saint John River in northern New Brunswick was on June 22, which coincided with the emergence of several other snaketails. The adults are rarely encountered close to where they emerged. The Pygmy Snaketail probably spends the bulk of its adult life in the forest canopy. It is likely that the adults fly for six to eight weeks following emergence, although some individuals survive for a few more weeks. The Pygmy Snaketail is preyed upon by insectivorous birds such as swallows and by large insects such as certain large dragonflies, wasps and flies. As with all dragonflies, larvae and adults are predaceous, principally eating invertebrates. Larvae may also take small fish.
The main threat to the species is habitat degradation, with larger rivers being especially susceptible to environmental damage. One particularly serious threat to populations is the impoundment of running waters, because the Pygmy Snaketail apparently cannot breed in conditions found below dams. Hydroelectric dam construction on the Namakan River is a threat to the Ontario population, but dam construction poses less of a threat to the New Brunswick populations. Water pollution caused by excessive nutrient input from sewage or by sedimentation due to agricultural or forestry runoff is a direct threat to larval habitat. Pesticides used in agriculture or forestry management, particularly those used for the control of aquatic larvae of biting insects, are a direct threat to larval success. Toxic chemical spills are also a threat, particularly where road and rail corridors are adjacent to the river. Because dragonflies are predators that feed largely on other predaceous invertebrates, they will take up insecticides persisting in their prey to a toxic level. Clearing and insecticidal spraying of forests surrounding their rivers may exert a negative impact on adult populations, which are thought to spend much of their time in the forest canopy. Any boat or vehicle that creates a wake during the hours of emergence cannot fail to kill emerging specimens. Even landing canoes, wading and walking along the shore at emergence sites is potentially damaging to the emerging population during the short emergence period. On the Saint John River at Baker Brook, a threat to larvae and emergents is the driving of heavy agricultural machinery through the river to work on the large island in mid-stream, even though the area influenced is small compared with the overall habitat. Certain introduced fish species represent a potential threat to the Pygmy Snaketail. For example, the Muskellunge, introduced in Quebec within the Saint John River watershed, could reach that river in New Brunswick and have a significant impact on larvae. Finally, alien invasive species can alter the habitat to the detriment of the Pygmy Snaketail. Invasive aquatic plants can grow to a density that seriously affects the water quality.
Federal ProtectionMore information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
The Pygmy Snaketail is not protected under any provincial legislation in Ontario or New Brunswick. Of the 12 confirmed sites in Canada, the St. Croix River in southwest New Brunswick is protected to some extent by the St. Croix International Waterway Commission. Much of the Miramichi River is managed as a salmon fishery, which protects the habitat of this pristine river.
Provincial and Territorial Protection
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
8 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- COSEWIC Assessments (1 record(s) found.)
- Response Statements (1 record(s) found.)
- Management Plans (1 record(s) found.)
- Orders (2 record(s) found.)
- COSEWIC Annual Reports (1 record(s) found.)
- Consultation Documents (1 record(s) found.)
COSEWIC Status Reports
COSEWIC Annual Reports
COSEWIC Annual Report - 2009 (2009)2009 Annual Report to the The Minister of the Environment and the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.
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