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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Caddisfly Genus Phryganea (Rush Sedges)

Trout may feed heavily on any stage of these large caddisflies.

Where & when

In 115 records from GBIF, adults of this genus have mostly been collected during August (35%), July (35%), June (20%), and September (7%).

In 67 records from GBIF, this genus has been collected at elevations ranging from 10 to 10157 ft, with an average (median) of 1027 ft.

Genus Range

source

Map of specific collection sites

Hatching behavior

The pupae crawl out onto shore to emerge, but it may be useful to imitate their subsurface movements.

Egg-Laying behavior

Time of day: Evening

The large adults have very unusual egg-laying behavior, described well by Gary LaFontaine in Caddisflies:

In the evening they begin the mating and egg-laying activities, the females flying thirty to forty feet up in the air and dive-bombing the surface. The large insects hit the water with such a force that they send up small splashes. During intense egg-laying activity they may make a smooth surface look rain splattered.

Swisher and Richards describe a different behavior for the genus in Selective Trout:

Females lay their eggs on the water's surface and run across the water to return to shore.

Readers familiar with this genus are encouraged to reconcile these conflicting accounts in the comments. It may be that both are correct, and the running behavior follows after the splash-down.