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 Suwallia (Sallflies)
Only Suwallia pallidula is known to be commonly encountered on trout streams.
Genus Range
Specimens of the Stonefly Genus Suwallia
2 Female Adults
I didn't key this one out under the microscope, but I just keyed a similar one from Montana and this one matches the macroscopic appearance closely enough that I'm guessing it's the same thing.
I collected a few of these throughout the afternoon. The positive ID on the adults allowed me to also put a species ID on the nymphs.
2 Adults
A large number of photos from the microscope allowed a fairly confident ID on this one, which not coincidentally matches very well a previous specimen of Suwallia pallidula that I collected in Washington.
2 Nymphs
This specimen keys out to Suwallia, for which I did not find any nymph species keys. However, I'm placing it in Suwallia pallidula because I caught a few adults in the same spot that closely resembled the abundant nymphs and keyed them out to species. Features I noted under the microscope when keying this specimen to genus included apical hairs of cercal segments that were directed at posterior angles, and the longest apical hairs of distal segments were shorter than their following segment.
Start a Discussion of Suwallia
Stonefly Genus Suwallia (Sallflies)
Taxonomy
Species in Suwallia
Suwallia forcipataForceps Sallflies
0
0
Suwallia pallidulaLittle Yellow Stoneflies
5
35
Species in Suwallia: Suwallia forcipata, Suwallia pallidula
6 species (Suwallia autumna, Suwallia dubia, Suwallia lineosa, Suwallia marginata, Suwallia sierra, and Suwallia wardi) aren't included.