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Species Stenacron interpunctatum

Big-Eyed Mayfly Nymph - Stenacron interpunctatum Heptageniidae (Flatheaded Mayfly), dorsal - Stenacron interpunctatum Mayfly Nymph - Stenacron interpunctatum bug eyed - Stenacron interpunctatum mayfly - Stenacron interpunctatum Ephemeroptera -- top right, Larinioides on head - Stenacron interpunctatum yellow mayfly - Stenacron interpunctatum flatheaded mayfly - Stenacron interpunctatum - female
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Ephemeroptera (Mayflies)
Suborder Pisciforma
Superfamily Heptagenioidea
Family Heptageniidae (Flatheaded Mayflies)
Genus Stenacron
No Taxon (interpunctatum complex)
Species interpunctatum (Stenacron interpunctatum)
Explanation of Names
Stenacron interpunctatum (Say 1839)
ID is very difficult. They cannot be ID'd reliably based upon tergal or sternal coloration. Removal of the left mandible and both maxillae are required for proper ID. The setae on the maxilla are commonly missing or broken so close inspection is necessary(1)
NA except sw. US(2) map(3)
Larvae are tolerant of a variety of current strengths and can occur in lentic habitats. They can be associated with undersides of large logs and boulders as well as leafy debris and gravel(1)
In Wisconsin -- Adults are usually found June-July but there is a late record of Sept(1)
Works Cited
1.Mayfly Larvae of Wisconsin
Tom H. Klubertanz. 2016. Board of Regents of the University of Wisconsin System.
2.Mayfly Central
3.Rohrbeck R. (2004-2014) Flyfishing entomology