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.

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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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Site updates from March 22, 2013

Closeup insects by Entoman from the Lower Yuba River in California

Female Skwala curvata (Large Springfly) Stonefly Adult

2 Pictures

Female Skwala curvata (Perlodidae) (Large Springfly) Stonefly Adult from the Lower Yuba River in California

This female dropped her eggs just before this photo was snapped. The distinctive notch in the subgenital plate identifies the species. An interesting observation is how active they get when exposed to direct sunlight. Trying to stage this specimen was most difficult. In the shade it would calm right down, but when exposed to direct sun it would immediately go nuts, scampering all over quickly without pause. Perhaps this explains why they don't seem to be found out and about on overcast days, but if the sun peeks out... She was 24 mm long, head to wingtip.

Collected March 21, 2013 from the Lower Yuba River in California

Added by Entoman on March 27, 2013

Collected March 21, 2013 from the Lower Yuba River in California and added by Entoman on March 27, 2013

Hesperoperla pacifica (Golden Stone) Stonefly Nymph

1 Picture

Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Nymph from the Lower Yuba River in California

This monster started to feed within a few minutes of sharing the inspection tray with its victims. This nymph is a voracious predator of small invertebrates and has even been noted for feeding on small fish and salmonid alevins. The niche it fills in fast water is equivalent to the Dragonfly nymphs that inhabit slower water.

Hesperoperla pacifica nymphs are easily distinguished from other western perlids by the presence of anal gills (obfuscated by algae in the tray) in combination with an hour glass shaped pale mark on the front of their heads.

Collected March 21, 2013 from the Lower Yuba River in California

Added by Entoman on April 4, 2013

Collected March 21, 2013 from the Lower Yuba River in California and added by Entoman on April 4, 2013