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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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Male Serratella micheneri (Little Dark Hendrickson) Mayfly Nymph Pictures

This specimen has tarsal claws with 7 denticles and tubercles on abdominal segments 4-7 only. It keys to Serratella micheneri, as do some other specimens from the same collection that lacked the dorsal stripe.

Ruler view of a Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington The smallest ruler marks are 1 mm.
Dorsal view of a Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington
Male Serratella micheneri (Ephemerellidae) (Little Dark Hendrickson) Mayfly Nymph from Mystery Creek #199 in Washington

This mayfly was collected from Mystery Creek #199 in Washington on July 28th, 2019 and added to Troutnut.com by Troutnut on July 30th, 2019.

Discussions of this Nymph

Ephemerella tibialis
2 replies
Posted by Millcreek on Dec 24, 2019
Last reply on Dec 26, 2019 by Millcreek
This nymph appears to be Ephemerella tibialis formerly known as Serratella tibialis. Check out Allen and Edmunds; http://www.ephemeroptera-galactica.com/pubs/pub_a/puballenr1963p583.pdf

Also check https://bugguide.net/node/view/696565/bgpage and https://bugguide.net/node/view/876178

Edit: Just noticed the other two Serratella micheneri sets of photos. These also appear to be Ephemerella tibialis.

Also spotted these two sets of photos where you identified the same or a similar nymph as Ephemerella tibialis.

http://www.troutnut.com/specimen/1176

http://www.troutnut.com/specimen/1178

Start a Discussion of Nymph

Male Serratella micheneri (Little Dark Hendrickson) Mayfly Nymph Pictures

Collection details
Location: Mystery Creek #199, Washington
Date: July 28th, 2019
Added to site: July 30th, 2019
Author: Troutnut
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