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.

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.

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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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Baetis (Blue-Winged Olive) Mayfly Nymph Pictures

Ruler view of a Baetis (Baetidae) (Blue-Winged Olive) Mayfly Nymph from Cayuta Creek in New York The smallest ruler marks are 1 mm.

Ventral view of a Baetis (Baetidae) (Blue-Winged Olive) Mayfly Nymph from Cayuta Creek in New York

Dorsal view of a Baetis (Baetidae) (Blue-Winged Olive) Mayfly Nymph from Cayuta Creek in New York

Baetis (Baetidae) (Blue-Winged Olive) Mayfly Nymph from Cayuta Creek in New York

This mayfly was collected from Cayuta Creek in New York on April 14th, 2007 and added to Troutnut.com by Troutnut on April 22nd, 2007.

Discussions of this Nymph

Baetidae

4 replies

Posted by Earlfishman on Apr 23, 2007

Last reply on Apr 24, 2007 by Konchu

This one looks like an almost ready to emerge male Baetis sp., but I can't be 100% based on the pictures and I definitely can't go any further than that.

As a side note, if anyone is interested in a good key to the larvae of Baetidae, search google for "EPA photographic Baetidae key" and click on the PDF at the EPA site (direct link to the PDF here). The key has some good photos and works very well for the eastern U.S.

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