Brook Snaketail Dragonfly
The beautiful brook snaketail dragonfly is listed as a species of special concern in New Jersey.
The beautiful brook snaketail dragonfly (Ophiogomphus aspersus) is listed as a species of special concern in New Jersey. A Threatened status listing has been proposed by the Endangered and Nongame Species Advisory Committee; however, no formal rule proposal has been filed to date.
In what is hoped will be the first of many articles about odonates (dragonflies and damselflies), I would like to highlight the beautiful brook snaketail dragonfly (Ophiogomphus aspersus). The Latin root Ophio means snake-like or serpent, hence the very appropriate common name applied to this group. The snaketails were given this name because males have sinuous or snake-like claspers at the end of the abdomen which are used during mating.
Snaketail adults usually emerge from rivers and streams from late May to early June in New Jersey. They are generally active through mid-June though stragglers have been observed into August. Five species of this group have been reported in our state although one has not been observed since the early 20th century. These are among the most environmentally sensitive dragonflies in North American and as such are outstanding indicators of water quality and overall watershed health.
Snaketails belong to the greater clubtail family (the Gomphids). All clubtails have widely spaced eyes that do not touch at any point. Most have a widening at the tip of the abdomen, also called a club. While most clubtails have simple patterns or dull coloration, the snaketails are mostly bright green. Other color patterns vary subtly, but they are stunning insects and among our most beautiful dragonflies. The majority of clubtails inhabit rivers and streams.
Many North American species are declining or are severely imperiled due to water quality degradation. Toxic run-off, siltation from erosion and the construction of dams are among the greatest threats facing clubtails and other odonates. The snaketails are generally the most sensitive to any environmental changes. Even minor increases in the silt or mud content in streams can alter dissolved oxygen levels and harm or kill snaketail larvae. Like most odonates, snaketails also need undisturbed fields and wooded uplands adjacent to breeding waters. It is here that critical foraging and breeding occurs. This habitat also provides vital shelter for fragile newly emerged adults during severe weather events and protects them from predators.
Toxic run-off, siltation from erosion and the construction of dams are among the greatest threats facing clubtails and other odonates.
Of the four snaketail species known to breed here, the rarest is the brook snaketail. The first New Jersey colony was not discovered until 1986 in the Whippany River watershed in Morris County. Since then, an additional four colonies have been found in the Skylands and Ridge and Valley regions. This highly localized species also inhabits small segments of the Musconetcong, Wallkill and Flat Brook watersheds.
The brook snaketail has very specific habitat requirements while the other three related species are slightly more elastic. This species inhabits clean, relatively quiet or slow moving streams with an abundance of sandy sediments. It shares this habitat requirement with the federally endangered dwarf wedgemussel and co-exists with it at two locations in New Jersey. It is often associated with the harpoon clubtail (Gomphus descriptus) and river jewelwing (Calopteryx aequabilis). The individual populations of brook snaketail in New Jersey are referred to as colonies due to the limited amount of appropriate habitat in our area. Unlike more common or generalized species, breeding is restricted to relatively small sections of the rivers and streams they inhabit.
Due to the many challenges facing this species, and the small size of the five known colonies, the brook snaketail has been proposed as a threatened species in New Jersey. This species will be carefully monitored to ascertain whether its status is changing. Further colonies are also being sought, particularly in the Ridge and Valley region. A study will be undertaken next year that will hopefully quantify the actual distance from breeding streams that this species travels while foraging. This information will eventually allow for the establishment of effective protective buffers around known brook snaketail colonies and their critical habitat areas.
written by Allen Barlow
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