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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 Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
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 velox (Brown Dun) Mayfly Nymph Pictures

These two exuviae are my sad little consolation prize after collecting a couple of really cool, large, mature mayfly nymphs I didn't recognize from a tiny, probably fishless, spring-fed tributary of a slightly less tiny trout stream. I saw the nymphs in the kicknet samples and carefully transferred each one to my holding cooler before going to collect more samples. When I got home, I carefully went through the whole sample and couldn't find either one of them. Getting worried, I did it again and even more carefully. This time, I found both exuviae. By process of elimination, pretty much the only possibility is that both of them hatched out of my cooler and flew away during the 10 minutes or so that I had the lid off to collect more samples.

I was really excited about them for the whole three-hour drive home and seriously bummed that they disappeared. In the field I thought they might be one of the families of swimmer nymphs I don't have yet, like Ametropodidae, but keying the exuviae takes me to Ameletus, so at least I didn't miss some great rarity. Still, they were much larger and darker than any other Ameletus I've collected and probably a species I don't have yet.

Edit: I returned four years later and caught a specimen of Ameletus velox in this spot (actually several, just photographed one), which I think solves the mystery of this one's ID.

Lateral view of a Ameletus velox (Ameletidae) (Brown Dun) Mayfly Nymph from Mystery Creek #199 in Washington
Ruler view of a Ameletus velox (Ameletidae) (Brown Dun) Mayfly Nymph from Mystery Creek #199 in Washington The smallest ruler marks are 1 mm.

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.


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Ameletus velox (Brown Dun) 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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