Ophiogomphus howei Bromley, 1924
Basis for Listing
Snaketails (Ophiogomphus spp.) occur primarily in the north, with the greatest global diversity of species being in North America. Pygmy Snaketails (Ophiogomphus howei) are known from the Appalachian Mountains of Tennessee through New Brunswick and from the Upper Great Lakes region. The Upper Great Lakes population of this species is about 450 miles (725 km) disjunct from the eastern population. It has been reported primarily from Wisconsin, with a few records in the Upper Peninsula of Michigan, one record in Northwestern Ontario, and from four counties in Minnesota: Pine, Chisago, Kanabec, and Itasca (Laurentian Mixed Forest Province) (Odonata Central 2017).
This diminutive snaketail species inhabits large rivers in predominately forested watersheds that are characterized by large water volumes, stable flows, and high water quality. The larvae develop in cobble and gravel substrate and are sensitive to siltation, run-off, river impoundments, and channelization. The paucity of rivers that meet this description in Minnesota limits the Pygmy Snaketail’s breeding options to a handful of waters in the state. For these reasons, the Pygmy Snaketail was designated of special concern in 2013.
The Pygmy Snaketail is the smallest of the snaketails, with the adults averaging about 3.3 cm (1.3 in.) long. Like other snaketails, Pygmy Snaketails have a bright green thorax, with some black vertical striping. The face is green and unstriped, hind wings are bright yellow from the bases out at least to the halfway point, legs are black. Abdominal segments 3-7 have variously sized yellow triangles, with segments 8-10 having reduced yellow markings or no markings at all. Females have short black occipital (at the top of the head, between the eyes) horns (Paulson 2012).
The Pygmy Snaketail prefers larger pristine rivers that have regions of low gradient, with substrates of fine sand and pea-sized gravel. Breeding waters are in forested regions, as the adults forage in adjacent forests. Dams produce conditions, both upstream and downstream, that are unsuitable for larval survival (Dunkle 2000). The species has been determined to be a good indicator of water quality (Legler et al. 2013). Very little is known about this species' larval life cycles or habits.
Biology / Life History
Adults forage in wooded portions of the breeding waters, typically not flying far afield, and probably spending much of their time feeding at treetop level. Males make short aggressive patrol runs over swiftly flowing water, returning quickly into the nearby forest. Females lay eggs in the same swift waters, apparently unguarded by the males, ovipositing while flying a large circular beat across the water’s surface (Paulson 2012). Very little is known about this species' larval life cycles or habits.
Conservation / Management
It has been noted that Pygmy Snaketails cannot tolerate water conditions either below or above dams in rivers (Dunkle 2000). Deforestation or inadequate agricultural safeguards within the watershed can lead to loss of foraging grounds for adults and to siltation of the larval habitat. Adults are on the wing for a short period from mid-June to mid-July and are indiscriminate predators of flying insects.
Conservation Efforts in Minnesota
Pygmy Snaketails occurring along the St. Croix River are afforded protection by the National Park Service, which designated it a National Scenic Riverway. They are also protected in St. Croix, Wild River, and Interstate state parks and Franconia Bluffs Scientific and Natural Area.
The non-profit Minnesota Dragonfly Society is looking for the Pygmy Snaketail (among many other species of Odonata) throughout Minnesota through surveys and educational workshops. These surveys are conducted by volunteers and are supported through an Enbridge Ecofootprint Grant through 2018.
Kurt Mead (MNDNR), 2018
(Note: all content ©MNDNR)