Plants and Animals

Epeorus suffusus A mayfly

Key Characteristics

Adult mayflies of the Epeorus genus have a wing length between 7 and 19 mm. The eyes are quite large and, in the male, forelegs are as long or longer than body length. Epeorus nymphs have a generally flattened appearance, with two tales and a body length of 7-17 mm. Head shape is trapezoidal, being wider at the front. The legs are long, with flattened, wide femurs, each typically marked with a single large brown dot on the dorsal side. Plate-like gills are present on body segments 1-7. The thorax of Epeorus suffusus is a dull brown, with the posterior portions of a darker shade. The legs and tails are a pale yellow color.

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G1Q - Critically imperiled. Questionable taxonomy that may reduce conservation priority
State Rank: SNA - Not applicable (element is not a suitable target for conservation)


CountyNumber of OccurrencesYear Last Observed

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


Epeorus nymphs inhabit areas of rapidly flowing water in cool, shallow streams, where they can be found clinging to rocks or sticks (Edmunds et al. 1976).

Natural Community Types

  • Headwater stream (1st-2nd order), riffle
  • Headwater stream (1st-2nd order), run
  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

The major threats to mayfly diversity and abundance stem from habitat degradation and compromised water quality. Among the most sensitive of aquatic insect groups, mayfly populations have suffered significant impacts due to stream acidification (Earl and Callaghan 1998, New 1998), the presence of industrial pollutants, and pesticide applications targeting other species (Williams and Feltmate 1992). Minimizing these threats, as well as reducing siltation from run-off and construction projects, will aid in maintaining healthy nymph habitat. As little published information regarding Epeorus suffusus is currently available, further research into the biology, distribution and habitat requirements of this species may illuminate additional management strategies.

Active Period

Breeding from first week of June to fourth week of June

Survey Methods

Adult mayflies can be sampled from mating swarms using a long-handled, fine-mesh nylon net (Leonard and Leonard 1962). There are several methods used to collect nymphs, including substrate sampling using an Ekman or Petersen grab, d-frame net, or naturalists' dredge. Gathering of river stones by hand is another successful method. Collected samples are then rinsed through a series of sieves and specimens hand-picked using forceps (New 1998).

Aerial net, visual survey

Survey Period: From first week of June to fourth week of June

Survey Method Comment: Adults


Survey References

  • Leonard, J.W. and F.A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science, Bloomfield Hills, MI. 139pp.
  • New, T.R. 1998. Invertebrate Surveys for Conservation. Oxford University Press, New York. 240pp.
  • Schwiebert, E.G. 2007. Nymphs Volume II: Stoneflies, Caddisflies, and Other Important Insects Including the Lesser Mayflies. The Lyons Press, Guilford, CT. 795pp.

Technical References

  • Caucci, A., B. Nastasi, A. Flick and N. Lyons. 2004. Hatches II: A Complete Guide to the Hatches of North American Trout Streams. The Lyons Press, Guilford, CT. 341 pp.
  • Earle, J. and T. Callaghan. 1998. Impacts of mine drainage on aquatic life, water uses, and man-made structures. Pp. 4.1-4.10. In: Brady, B.C., T. Kania, W.M. Smith and R.J. Horberger (eds.). 1998. Coal Mine Drainage Prediction and Pollution Prevention in Pennsylvania. Pennsylvania Department of Environmental Protection.
  • Edmunds, G.F. Jr., S.L. Jensen, L. Berner. 1976. The Mayflies of North and Central America. University of Minnesota Press, Minneapolis, MN. 329 pp.
  • Leonard, J.W. and F.A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science, Bloomfield Hills, MI. 139pp.
  • Needham, J.G., J.R. Traver and Y. Hsu. 1935. The Biology of Mayflies. Comstock Publishing, New York. 759 pp.
  • Williams, D.D. and B.W. Feltmate. 1992. Aquatic Insects. C.A.B. International, Wallingford, U.K. 358pp.