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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
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.

Dorsal view of a Holocentropus (Polycentropodidae) Caddisfly Larva from the Yakima River in Washington
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.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Ameletus (Brown Dun) Mayfly Nymph Pictures

Ventral view of a Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Dorsal view of a Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ruler view of a Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington The smallest ruler marks are 1 mm.
Lateral view of a Ameletus (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington

This mayfly was collected from the South Fork Snoqualmie River in Washington on June 13th, 2019 and added to Troutnut.com by Troutnut on June 14th, 2019.

Discussions of this Nymph

Siphlonurus sp.
1 replies
Posted by Millcreek on Jan 27, 2020
Last reply on Feb 2, 2020 by Troutnut
This looks more like an Ameletus species than a Siphlonurus species. At any rate it isn't Siphlonurus because it dosen't have double gills on any segments.

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Ameletus (Brown Dun) Mayfly Nymph Pictures

Collection details
Location: South Fork Snoqualmie River, Washington
Date: June 13th, 2019
Added to site: June 14th, 2019
Author: Troutnut
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