Blue-winged Olives
Baetis
Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
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This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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Landscape & scenery photos from Silver Creek
On-stream insect photos from Silver Creek
Closeup insects by Troutnut from Silver Creek in Idaho
Some notes from identifying this specimen under the microscope:
1. The hind wing has three longitudinal 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.
1. The hind wing has three longitudinal 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.
This female spinner was deceased when photographed, so the posture is unnatural, but it was a substantial hatch and clearly worth imitating (with wet flies to imitate the sunken ovipositing females) so I went ahead with the photos.
It was collected in association with a male spinner.
It was collected in association with a male spinner.