- Scientific name: Phanogomphus quadricolor
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Endangered (MA Endangered Species Act)
Description
Male rapids clubtail
The rapids clubtail (Phanogomphus quadricolor) is a large, slender insect belonging to the order Odonata, suborder Anisoptera (the dragonflies), and family Gomphidae (the clubtails). The clubtails are a large, diverse group of dragonflies named for the lateral swelling at the tip of the abdomen that produces a club-like appearance which varies greatly among species. Clubtails are further distinguished from other dragonflies by their widely separated eyes, wing venation characteristics, and behavior. The rapids clubtail belongs to the genus Phanogomphus (American clubtails) that are characterized by their dull coloring of grays, greens, browns and blacks, and by their relatively small clubs. Rapids clubtail has blue-green eyes, black legs, and dark body with pale yellow and green markings. The thorax (section behind the head) is marked with yellow to gray-green dorsal and lateral stripes. The abdomen (section behind the thorax) is black. Segments 1 through 7 have thin yellowish to gray-green dorsal stripes and lateral marks with relatively extensive yellow blotches on segments eight and nine. Recently emerged individuals are more brightly colored than mature individuals and can initially cause identification problems. Females are similar in coloration but have more extensive yellow markings on the abdomen and are stouter overall except for the club.
Adult rapids clubtails range in length from 42-45 mm (1.6 -1.8 in). The fully developed nymphs range from 22-28 mm (0.8-1.1 in).
Although one can fairly quickly recognize a clubtail as belonging to the genus Phanogomphus by a combination of factors, including its coloration and small club, members of this genus can be very difficult to identify to the species level. Examination of the terminal abdominal appendages of the male and the vulvar lamina of the female are the most reliable method for identification. Species with the most similar appearance include beaverpond clubtail (P. borealis) and harpoon clubtail (P. descriptus). Male rapids clubtail tend to have more extensive lateral markings on segments eight and nine and females have a lateral yellow spot on segment seven unlike beaverpond and harpoon clubtails. The nymphs and exuviae can be distinguished by characteristics of the labium as per the keys by Walker (1958), and Soltesz (1996), Needham et al. (2000), and Tennessen (2019).
Life cycle and behavior
Note, nymphs are present year-round.
Rapids clubtails are elusive and little is known about their life history. The egg and nymph life stages are fully aquatic. The nymphs are predators, feeding on a wide variety of aquatic insects, small fish, and tadpoles. Nymphs spend much of their time burrowing in the bottom sediment in depositional habitats that provide them protection from predators and camouflage to catch prey. Nymphs undergo several molts (instars) for at least 2 years until they are ready to emerge as winged adults. When ready to emerge, typically in late May, the nymphs crawl out onto exposed rocks, emergent vegetation, partially submerged logs, or the steeper sections of riverbanks, where they undergo transformation to adults (a process known as eclosion). Emergence generally takes place very early in the morning, presumably to reduce exposure to predation. The cast nymphal exoskeletons, known as exuviae, are identifiable to species and can be a reliable, useful means to determine the presence of a species.
As soon as the freshly emerged adults are dry and the wings have hardened sufficiently, they fly off to seek refuge in the vegetation of adjacent uplands. Here, they spend several days or more feeding and maturing, before returning to their breeding habitats. During this time of wandering and maturation, rapids clubtails can be found in fields and forest clearings, sometimes far away from the breeding site, perched horizontally on sunlit vegetation or the ground. From such perches, rapids clubtails make periodic feeding forays during which they consume small aerial insects such as flies and mosquitoes. When the maturation process is complete, the adults return to the stream to breed. In Massachusetts, the rapids clubtail breeds through the month of June. Although the nymphs are found in the quiet pools below areas of rapids, the adults prefer the swifter sections of the rivers. Upon returning to the stream, male rapids clubtails can be found perching on rocks in these areas or on shoreline vegetation. From exposed perches they make patrols out over the water, often returning to the same or a nearby perch. During these patrols, the males are primarily searching for mates and driving off any potential competitors. Females spend little time around the breeding habitat, except during the brief time when they are ready to mate and lay eggs. When mating is completed, the female returns to the water to deposit her eggs. Female rapids clubtails oviposit alone by tapping the tip of their abdomen to the surface of the water. This is usually done in the faster sections of the stream where there are rapids. Females fly rapidly back and forth over the water touching the surface of the water with the tip of her abdomen every few feet to release eggs. Upon being laid, it is likely that the eggs are carried downstream from the rapids and deposited in the pools where they hatch and the nymphs develop.
Rapids clubtail have a rather short flight season with emergence beginning in late May and early June and the adults flying into July.
Distribution and abundance
The rapids clubtail is found from southern Ontario south to Alabama and Georgia, west to Arkansas and Minnesota and north to Maine. The rapids clubtail has been recorded in each New England state. In Massachusetts, the species occurs in the Housatonic, Westfield, Middle Connecticut, Chicopee, and Merrimack watersheds. As with many species of clubtails, population densities appear to be low. This may reflect the elusiveness of the adults or low detection rates, and/or actual low population sizes with typically low exuviae collected and adults observed. Recent exuviae surveys have expanded its distribution within extant river systems along with new watersheds.
The rapids clubtail is listed as an Endangered species in Massachusetts. As with all species listed in Massachusetts, individuals of the species are protected from take (picking, collecting, killing, etc.) and sale under the Massachusetts Endangered Species Act.
Distribution in Massachusetts.
1999-2024
Based on records in the Natural Heritage Database.
Habitat
The rapids clubtail inhabits medium to large-sized streams typically with intermittent riffles and rapid mesohabitats and adjacent depositional areas. Substrates range from mud to cobble. Exuviae have been typically found on banks adjacent to depositional mesohabitats including pools and slow runs. The adults inhabit riparian areas, forested uplands, fields, and when mature are often flying over swifter currents around riffles.
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Medium-sized stream habitat for rapids clubtail.
Threats
Degradation of water quality, alteration of streamflows, and upland habitat loss are primary threats to spine-crowned clubtail. Potential threats to water quality include pollution and sewage overflow, salt and other road contaminant run-off, and siltation from construction or erosion. The disruption of natural flow regimes by flow regulation projects may have a negative impact on odonate populations. Extensive use of the river by power boats and jet skis that generate large wave action is a serious concern, particularly during the emergence period of rapids clubtail (as well as several other clubtail species). The potential impacts of climate change, including on streamflows and temperature, are unknown for rapids clubtail.
Conservation
Survey and monitoring
Recent efforts have expanded our knowledge of rapids clubtail distribution largely through exuvia surveys. Since adults can be difficult to detect because of their elusive behavior, exuvia not only provides increased detection but also site-specific locations of aquatic nymph and breeding habitat. Surveys may target adults in combination with exuviae but never alone. Robust stream populations should be routinely monitored every five years or to the extent practical to document changes in occupancy and habitat conditions. Effort should also target under-surveyed streams and stream segments identified as potentially suitable habitat. It’s possible the species occurs in more watersheds than currently known.
Management
Upland and stream habitat protection is critical for the conservation of rapids clubtail. Protection of forested upland borders of these river systems are critical in maintaining suitable water quality and are critical for feeding, resting, and maturation. Development of these areas should be discouraged, and the preservation of remaining undeveloped uplands should be a priority. Alternatives to commonly applied road salts should be tested to minimize freshwater salinization. Altered streamflows from hydroelectric operations should minimize rapid flow increases during emergence time to prevent mortalities. Hardened and channelized stream segments should be restored to promote natural sediment dynamics.
Research needs
Continued effort is needed to define habitat requirements, distribution, relative abundance, and potential breeding sites to update the species status in Massachusetts. Estimation of detection and occupancy rates and how other environmental variables (e.g., sample timing, weather) affect these rates for exuvia sampling is needed. Other research efforts include projections of species distribution under climate change scenarios and climate vulnerability analysis specifically in Massachusetts.
References
Dunkle, S.W. 2000. Dragonflies through Binoculars. Oxford University Press.
Lam, E. Dragonflies of North America. Princeton NJ: Princeton University Press, 2024.
Needham, J.G., M.J. Westfall, Jr., and M.L. May. 2000. Dragonflies of North America. Scientific Publishers.
Nikula, B., J.L. Ryan, and M.R. Burne. 2007. A Field Guide to the Dragonflies and Damselflies of Massachusetts. Massachusetts Natural Heritage and Endangered Species Program.
Paulson, D. Dragonflies and Damselflies of the East. Princeton NJ: Princeton University Press, 2011.
Soltesz, K. 1996. Identification Keys to Northeastern Anisoptera Larvae. Center for Conservation and Biodiversity, University of Connecticut.
Walker, E.M. 1958. The Odonata of Canada and Alaska, Vol. II. University of Toronto Press.
Tennessen, K. Dragonfly Nymphs of North America: An identification guide. Springer, 2019.
Contact
| Date published: | April 9, 2025 |
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