Plants and Animals

Anthopotamus verticis Walker's tusked sprawler

Key Characteristics

Mature individuals of this species are relatively small, averaging 7-11 mm in body length, with forewings of 8-12 mm. The eyes are large and black, the wings translucent, and the three tails are white with faint brownish joinings. The head and thorax, as well as the female abdomen, are pale yellow in color. In males, the abdomen is translucent. Large pink spots covering the abdomen in both sexes are diagnostic. In the subamigo (dun) stage, these spots are not visible and wings and tails are pale yellow. Walker's tusked sprawler nymphs average 10 to 13 mm in body length, and are covered with amber to brown mottlings. The abdomen features a reddish dorsal median stripe bordered by pale brown bands. The nymph's three tails are amber in color and the forked gills are grayish and heavily fringed (Schwiebert 2007). All Anthopotamus nymphs have well-developed mandibular tusks (McCafferty and Bae 1990).

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: SNR - Not ranked


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.


A species of medium to large rivers (Bright 2011), Walker's tusked sprawler nymphs prefer substrates of coarse gravel or small pebbles (Bae and McCafferty 1994).

Natural Community Types

  • Mainstem stream (3rd-4th order), pool
  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle
  • River (5th-6th order), pool
  • River (5th-6th order), run
  • River (5th-6th 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

As mayflies spend the majority of their lives as underwater nymphs, emerging only for a short adult period of several hours to a few days, maintaining high water quality is a management priority. Increased sedimentation negatively impacts mayfly species by covering gravel and pebble substrates and filling in the small spaces between stones in which they live (Williams and Feltmate 1992). Maintaining adequate riparian buffers, along with efforts to reduce agricultural/urban runoff and the siltation associated with major construction projects, will help to preserve mayfly habitat. Being among the most sensitive to low pH levels of any aquatic insect group, mayflies are typically the first to disappear from waters becoming increasingly acidified (Earle and Callaghan 1998). Initiatives aimed at reducing acid precipitation may therefore benefit this species. Additionally, drastic population declines caused by industrial pollution and pesticide applications aimed at other species have been well documented (Williams and Feltmate 1992). Not only aquatic insects, but a wide variety of organisms are affected by the degradation of freshwater systems. As the process of population recovery in formerly impacted areas can take many years, the protection of healthy waterbodies is key.

Active Period

Breeding from fourth week of May to fourth week of August

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 fourth week of May to fourth week of August

Survey Method Comment: Adults

D-frame net, dip net

Survey Period: From fourth week of May to fourth week of August

Survey Method Comment: Nymphs


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.

Technical References

  • Bae, Y.J. and W.P. McCafferty. 1994. Microhabitat of Anthopotamus verticis (Ephemeroptera: Potamanthidae). Hydrobiologia 288(2):65-78.
  • Bright, E. 2011. Aquatic Insects of Michigan: Potamanthidae. Accessed August 9, 2011.
  • 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.
  • Leonard, J.W. and F.A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science, Bloomfield Hills, MI. 139pp.
  • McCafferty, W.P. and Y.J. Bae. 1990. Anthopotamus, a New Genus for North American Species Previously Known as Potamanthus (Ephemeroptera: Potamanthidae). Entomological News 101(4): 200-202.
  • McCafferty, W.P. and Y.J. Bae. 1994. Life History Aspects of Anthopotamus Verticis (Ephemeroptera: Potamanthidae). The Great Lakes Entomologist 27(2):57-67.
  • Schwiebert, E.G. 2007. Nymphs Volume II: Stoneflies, Caddisflies, and Other Important Insects Including the Lesser Mayflies. The Lyons Press, Guilford, CT. 795pp.
  • Williams, D.D. and B.W. Feltmate. 1992. Aquatic Insects. C.A.B. International, Wallingford, U.K. 358pp.