Neartic
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Maccaffertium mediopunctatum
flat-headed mayfly
Maccaffertium mediopunctatum is a species of flat-headed mayfly in the family Heptageniidae. It occurs in Southeastern Canada and the Eastern United States. The species has two recognized subspecies: M. m. arwini and M. m. mediopunctatum. Like other members of its genus, it exhibits the unique mayfly developmental trait of having a fully winged subadult stage (subimago) that requires one additional molt to reach sexual maturity.