- Scientific name: Prostoia hallasi
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
Description
The swamp forestfly is a small slender insect belonging to the order Pelocoptera (stoneflies), family Nemouridae (forestflies or spring stoneflies) and genus Prostoia. Adults are dark with wings lying flat along abdomen when at rest. Adults are <9 mm (0.35 in) and nymphs are 5-6 mm (0.2-0.24 in) in length. Refer to keys from Grubbs et al. (2014) and Grubbs and Baumann (2023) for adults, Stewart and Stark (2002), Stewart and Stark (2008) and for nymphs and adults at the genus-level for definitive identification.
Life cycle and behavior
Little is known about the life history of swamp forestfly but can be inferred from species from shared genus, family, and/or order taxonomic levels. The life cycle of the swamp forestfly is 1-2 years consisting of an egg, nymph (i.e. larva), and adult life stages. Eggs cling to substrate via a gelatinous film and other stabilizing mechanism and may undergo diapause in summer or winter months. Eggs hatch into nymphs growing and molting for months. Nymphs are detritivores, shredding and consuming organic matter and can be found clinging to leaf packs and mosses in various mesohabitats. The nymphs emerge from the water onto stable substrate (e.g., rocks, vegetation) and transform into winged adults. Adults may be present from February to April, live for about 1-4 weeks, and disperse upstream, downstream, and into other streams (i.e., <1 km; 0.62 mi) within forested upland corridors. For reproduction, males mount females and release sperm internally or externally of the female’s genital pore. After mating occurs, females either release eggs over the water surface or dip their abdomens and deposit them into the water.
Distribution and abundance
The swamp forestfly range has been recorded in Massachusetts, Connecticut, Virginia, North Carolina, and Illinois. In Massachusetts, the species was recorded in eastern half of the state at unknow location. The species distribution and abundance are data deficient in Massachusetts. Elsewhere, the species has been recorded at low abundances and at few and scattered localities in its range. Swamp forestfly is a 2023 Regional Species of Greatest Conservation Need of high conservation concern.
Habitat
Swamp forestfly inhabits small to moderate-sized streams within the Atlantic coastal plain. The nymphs are detritivores and occur in leaf packs and mosses in depositional and erosional stream habitat patches.
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Threats
Degradation of water quality, alteration of streamflows, and upland habitat loss are primary threats to swamp forestfly. Potential threats to water quality include pollution and sewage overflow, salt and other road contaminant run-off, herbicides and pesticides, and siltation from construction or erosion. The disruption of natural flow regimes by water withdrawals, damming, and stream channelization may have a negative impact on populations. Warming stream temperatures and changes to precipitation regimes from climate change may reduce suitable habitat. Additional threats illegal or accidental industrial discharge and hardening of channel banks and siltation that creates unstable stream habitat.
Conservation
Survey and monitoring
Standardized and targeted surveys for swamp forestfly is needed to determine its status in Massachusetts. Surveys should target stream sites to determine species occupancy and population status, particularly in western Massachusetts. Multiple site visits (e.g., ≥3) may be required to detect this species. Routine monitoring of prioritized sites is needed estimate occupancy trends overtime.
Management
Upland and stream habitat protection is critical for the conservation of swamp forestfly. 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 tested to minimize freshwater salinization. Hardened and channelized stream segments should be restored to promote natural sediment dynamics.
Research needs
Through standardized surveys, effort is needed to define habitat requirements, distribution, relative abundance, phenological timing (e.g., adult emergence), and breeding sites. Research effort is needed to estimate detection and occupancy rates and how other environmental variables (e.g., sample timing, weather) affect these rates. Other research efforts include projections of species distribution under climate change scenarios and climate vulnerability analysis in Massachusetts.
References
Beaty, S. R. 2015. The Plecoptera of North Carolina: A Biologist’s Handbook for the Identification of Stonefly Nymphs with Standard Taxonomic Effort Levels. Version 4.0. North Carolina Department of Environmental Quality, Division of Water Resources, Biological Assessment Branch. Raleigh, North Carolina. iv + 91 pp.
DeWalt RE, Hopkins H, Neu-Becker U, and Stueber G. Prostoia hallasi Kondratieff & Kirchner, 1984. Plecoptera Species File. Retrieved on 2025-04-08 at https://plecoptera.speciesfile.org/otus/891592/overview
Grubbs, S.A., and R.W. Baumann. 2023. The Nemourinae (Insecta, Nemouridae) of the eastern Nearctic. Zootaxa 5306(1):001-053.
Grubbs, S.A., R.W. Baumann, R.E. Dewalt, T. Tweddale. 2014. A review of the Nearctic genus Prostoia (Ricker) (Plecoptera, Nemouridae), with the description of a new species and a surprising range extension for P. hallasi Kondratieff & Kirchner. ZooKeys 401:11-30.
Kondratieff, B.C., and R.F. Kirchner. 1984. A new species of Nemouridae (Plecoptera) from the Great Dismal Swamp, Virginia, USA. Proceedings of the Entomological Society of Washington 86(3):578-581.
Macneale, K.H., Peckarsky, B.L., G.E. Likens. 2005. Stable isotopes identify dispersal patterns of stonefly populations living along stream corridors. Freshwater Biology 50:1117-1130.
Stewart, K.W. & Stark, B.P. 2002. Nymphs of North American Stonefly Genera (Plecoptera). Second Edition. the Caddis Press. Columbus, Ohio, xii + 510 pp.
Stewart, K.W., and B.P. Stark. 2008. Ch. 14 Plecoptera in R.W., Merritt, Cummins, K.W. and Berg, M.B., Eds. 2008. An Introduction to the Aquatic Insects of North America. Kendall/Hunt Publishing Co., Dubuque, Iowa.
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| Date published: | April 11, 2025 |
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