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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Epeorus albertae (Heptageniidae) (Pink Lady) Mayfly Nymph from the East Fork Issaquah Creek in Washington
This specimen keys to the Epeorus albertae group of species. Of the five species in that group, the two known in Washington state are Epeorus albertae and Epeorus dulciana. Of the two, albertae has been collected in vastly more locations in Washington than dulciana, suggesting it is far more common. On that basis alone I'm tentatively putting this nymph in albertae, with the large caveat that there's no real information to rule out dulciana.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Species Macdunnoa persimplex

Where & when

In 4 records from GBIF, adults of this species have been collected during July (50%), May (25%), and June (25%).

In 1 record from GBIF, this species has been collected at elevation of 4948 ft.

Species Range

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Male Spinner

Described in Needham et al (1935) as Heptagenia persimplex
Body length: 7 mm
Wing length: 7.5 mm

A small pale species; genitalia distinctive; it may be allied to Heptagenia elegantula (see fig. 95).

Eyes widely separated; vertex of head between eyes bright yellow, becoming pale creamy below antennae. Thorax creamy; yellowish tinges on pleura or bases of fore legs. Legs pale yellowish, shading into dirty whitish on tibiae and tarsi. Fore tibia smoky at apex; fore tarsus distinctly longer than tibia; basal tarsal joint normally about 1/3 the length of the second; second subequal to third, twice as long as fourth; fifth about as long as first. Considerable variation exists, in different specimens, however, as to the relative lengths of the fore tarsal joints. Wings hyaline; cross veins dark. 5 to 6 basal costal cross veins; stigmatic cross veins somewhat thicker than the others, but not as much so as in Anepeorus simplex (now a synonym of Spinadis simplex) which is superficially very similar to the present species.

Abdomen pale creamy; segments 1-7 hyaline, 8-10 opaque. Tails whitish. Apical margin of forceps base rather deeply excavated; penes slightly resemble those of H. elegantula on the one hand, and those of the H. lucidipennis (now a synonym of Nixe lucidipennis) group on the other. Forceps joints, however, as in the former species.

Start a Discussion of Macdunnoa persimplex


  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Macdunnoa persimplex

Species Range
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