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.
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
Mayfly Species Eurylophella verisimilis (Chocolate Duns)
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
Wing length: 8 mm
A species of the bicolor group (now a synonym of Eurylophella bicolor), intermediate between E. bicolor (now a synonym of Eurylophella bicolor) and E. temporalis (now a synonym of Eurylophella temporalis); abdominal sternites darker and legs deeper yellow than in these species. Occipital tubercles of nymph well developed; rows of dorsal spines evenly divergent to rearward.
Eyes orange. Head reddish brown with purplish brown shading around the ocelli. Thorax deep brown. Legs rather bright yellow, with traces of orange patches at the base, the middle and the apex of each femur. Wings hyaline, venation hyaline. Abdominal tergites deep brown, with no indication of yellow or orange shading. Abdominal sternites darker than in bicolor or temporalis. Faint indications of the usual dark dots and oblique streaks. Tails smoky, the joinings narrowly darker.
Nymph
The occipital tubercles of the nymph are quite well developed in both sexes. The rows of dorsal spines are gradually and evenly divergent to rearward; those of tergites 1-3 are slightly longer and more erect than in E. bicolor, the tips more pointed. The postero-lateral spines on segments 2 and 3 are considerably better developed than in bicolor (now a synonym of Eurylophella bicolor). Tails brown with no pale bands.
Start a Discussion of Eurylophella verisimilis
References
- Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.
Mayfly Species Eurylophella verisimilis (Chocolate Duns)
Species Range
Common Name
Resources
- NatureServe
- Integrated Taxonomic Information System
- Global Biodiversity Information Facility
- Described by McDunnough (1930)