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.
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As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 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.
— 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.
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Stonefly Genus Acroneuria (Golden Stones)
This abundant genus has three important East/Midwest species. The superabundant species in the West have been moved to the new genera Calineuria and Hesperoperla.
Genus Range
Identification
To determine whether a specimen of Perlidae belongs to Acroneuria, use the Key to Genera of Perlidae Nymphs.
Specimens of the Stonefly Genus Acroneuria
1 Female Adult
6 Nymphs
The presence of anal gills, large dark spot in the center of the pale occipital bar point to lycorias.
Start a Discussion of Acroneuria
References
- Schwiebert, Ernest G. 1955. Matching the Hatch. MacMillan Publishing Company.
Stonefly Genus Acroneuria (Golden Stones)
Taxonomy
Species in Acroneuria
Acroneuria abnormisCommon Stone
3
32
Acroneuria arenosaEastern Stone
0
0
Acroneuria carolinensisCarolina Stoneflies
1
3
Acroneuria kosztarabiVirginia Stone
0
0
Acroneuria lycoriasBoreal Stoneflies
3
29
Species in Acroneuria: Acroneuria abnormis, Acroneuria arenosa, Acroneuria carolinensis, Acroneuria kosztarabi, Acroneuria lycorias
10 species (Acroneuria arida, Acroneuria evoluta, Acroneuria filicis, Acroneuria flinti, Acroneuria frisoni, Acroneuria hitchcocki, Acroneuria internata, Acroneuria ozarkensis, Acroneuria perplexa, and Acroneuria petersi) aren't included.