Mayfly Species Heptagenia culacantha

Where & when

In the paper announcing its discovery, this mayfly was reported only from two very large rivers in New York and Pennsylvania, the Delaware and the Susquehanna. The authors first discovered the nymphs and duns in the Susquehanna near Three Mile Island, PA in 1980, and in 1982 they found more nymphs which they raised into eight spinners. They later figured out that several specimens collected from the Delaware and Susquehanna in 1974 belonged to this new species.

This mayfly is very hard to find, even for experts who know where to look. The discovering scientists wrote, "rarely was more than one nymph found on the underside of the same rock." Their attempt to find more specimens in 1981 was unsuccessful. However, the species seems to still be around. The Mayflies of the United States geographic database shows additional records from far northeastern New York and south-central Pennsylvania.

Delaware River fishing guide Paul Weamer of Border Water Outfitters found and photographed a female Heptagenia culacantha dun in 2005, and his photos are posted and discussed in a "name that mayfly" contest on the Fly Fisherman magazine forum. Heptagenia flavescens was incorrectly suggested, but it wasn't far off the mark: Evans (1985) mentions that it is Heptagenia culacantha's closest relative.

Nymph biology

The nymphs are supposed to be strikingly colored yellow with brown markings. The scientific description brings to mind a color pattern similar to the Perlidae (golden stoneflies).