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The Specimen

Baetis tricaudatus (Blue-Winged Olive) Mayfly SpinnerBaetis tricaudatus (Blue-Winged Olive) Mayfly Spinner View 12 PicturesSome notes from identifying this specimen under the microscope:

1. The hind wing has three longitudinal veins (Longitudinal vein: Longitudinal veins are the major long veins running length-wise through an insect's wing, connecting the base to the outer margin, or the major branches from those veins.), but the third is faint, short (about half the length of the wing), and close to the wing margin.
2. Then antenna is brown fading into white at the tip, and the base is ringed with white.
3. The joints of the tarsal segments on the middle and hind leg have fine black markings.

It was also collected in association with a female spinner.
Collected September 4, 2020 from Silver Creek in Idaho
Added to by on September 18, 2020

The Discussion

TroutnutNovember 6th, 2020, 8:16 pm
Bellevue, WA

Posts: 2737
Does anyone here know any decent resources for identifying adult Baetis? I haven't found much.

This specimen sure seems to nicely fit the original description of Baetis alius adults. But I can't find very precise descriptions (let alone a key) for flavistriga and tricaudatus, both of which are other likely options given the location.

These made for a good fishable hatch on Silver Creek, so it sure would be nice to know what they are.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist

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