The Pygmy Snaketail (Ophiogomphe de Howe*, Ophiogomphus howei) is the smallest of a group of species that are characteristic of fast moving water. Even the largest species in this group are of only medium size for North American dragonflies (Anisoptera). The genus is in the Clubtail family (Gomphidae). There are no proposed subspecies or forms.
The adult appearance is typical of the genus except in size and wing markings. Their colour is black with vivid yellow markings on the abdomen and bright green on the thorax. The wings of both sexes are strongly marked basally with a large, transparent yellow-orange field. This is unique in the Clubtails, and rare among North American Odonata in general.
The larvae are small and cryptic, though readily determined in later stadia by the absence of dorsal abdominal hooks. Exuviae (skins abandoned after emergence) are the most often found evidence of the species.
The Pygmy Snaketail is largely confined to eastern North America. It is known in a line along the Appalachian Mountains from northern New Brunswick to southeast Tennessee. There is an apparently disjunct centre of distribution of the species in Michigan, Minnesota, Wisconsin and northwestern Ontario.
There are 12 known locales for the species in Canada. Canadian locations are in New Brunswick (11) and Ontario (1). It was first reported for Canada from the banks of the Saint John River in northern New Brunswick in 2002. The US border sites are on the St. Croix River in southwest New Brunswick. It also occurs on the Magaguadavic, Miramichi and Salmon Rivers.
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. This suggests that the larvae live on or within fine sand or pea gravel substrate where the current is strong. Searches for larval skins at many seemingly appropriate waters, and at the appropriate time of the year, have generally yielded no results for the species. It is believed to be absent from these waters; suggesting that the habitat, including factors influencing larval success and emergence locale, should be more narrowly defined than we currently realize.
As with all dragonflies, larvae and adults are predaceous, principally eating invertebrates. Larvae may also take small fish. There is no firm evidence of the length of time required for the larvae to develop to emergence; however, it is believed to take at least two years.
Emergence is largely associated with the synchronous emergence of other members of its genus. In 2002, emergence on the Saint John River in northern New Brunswick was on June 22, and was accompanied by emergence of several other Snaketails. In southwest New Brunswick, emergence is more likely near the beginning of the second week of June. It is likely that the adults fly for six to eight weeks following emergence, although some individuals survive for a few more weeks.
The adults are rarely encountered at water and are usually difficult to identify in flight. It is likely that they spend much of their flight in the canopy of the forest, which is the case with most Snaketails.
Population sizes and trends
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 hundreds of individuals are likely necessary to sustain a population. The data in hand is insufficient to speculate on fluctuation of population.
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.
Larvae of this species require clear, rapid, and unpolluted running waters, with the appropriate substrate believed to be fine sand or pea gravel. They usually occur in large rivers. Dam construction is a threat to the Ontario population but less of a threat to the New Bruswick populations. Water pollution due to excessive nutrient input from sewage, or sedimentation due to agricultural or forestry run-off are distinct threats to larval habitat. Pesticides and herbicides are also potentially threatening. Invasive species can alter the biota to the detriment of the Pygmy Snaketail.
Special significance of the species
This species’ presence is indicative of reasonably uncompromised running waters habitats. It is considered rare or at risk, and a protection priority, throughout its range. Organized and widespread inventory of dragonflies has occurred over the past two decades in both New Brunswick and Ontario, the only provinces in which it is recorded, with the results of this work indicating that it is very rare in both provinces.