An Update on the Occurrence of Three Species of Mayflies (Ephemeroptera) in Maine

Abstract

Mayflies, members of the order Ephemeroptera, are a diverse group of aquatic insects. Unlike many kinds of insects that spend most of their lives on land, mayflies spend most of their lives in the water as immature forms called nymphs. Adult mayflies are short lived and reproduce soon after they complete their development to the final winged stage called an imago. Mated adult females deposit their eggs in the waters of streams and ponds, where they hatch. After hatching, nymphs live on or among the sediments and submerged stems of aquatic plants. Nymphs can feed and grow for as much as two years before they complete their development to the first winged stage called a subimago, but often this development is accomplished in one year or less. The subimago is a winged terrestrial form that usually flies away from the water to a place of safety where it soon sheds its skin and becomes the imago. For further details of mayfly biology the reader is directed to publications by Edmunds et al. (1976) and McCafferty (1981). In the late 1980's an extensive survey of Maine's mayfly fauna was conducted (Burian and Gibbs 1990). The results of that work showed Maine to have a diverse mayfly fauna with a majority of its 160 species broadly distributed from the mountains of the Moosehead Plateau to the coast. However, about 41 species (26% of the fauna) were recorded from less than three sites. Species such as these may indeed be rare, endemic, or indicative of special habitats. But, they may have been simply overlooked at other sites or were collected in a life stage that could not be determined to species. In general, mayflies with few records have ranges and habitat requirements that are largely unknown. For these species each new record improves our understanding of its range and habitat. This is especially important for the purpose of habitat management and conservation because critical decisions, usually involving rare species, cannot be made without basic range and habitat information. In this paper new locality records are presented for Siphlonurus securifer McDunnough, Metretopus borealis Eaton, and Hexagenia rigida Eaton, which have few known localities in Maine. Siphlonurus