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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 Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Larva from the Yakima River in Washington
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae 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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True Bug Family Corixidae (Water Boatmen)

Dorsal view of a Corixidae (Water Boatman) True Bug Adult from unknown in Wisconsin
Water boatmen are very common in trout streams, but they aren't an important prey for most trout most of the time. Occasionally they are the important prey and trout feed on them selectively. This is especially likely in weedy mountain lakes and spring ponds.

Where & when

Time of year : Mating in early spring

Preferred waters: Most abundant in slow or still weedy waters

Boatmen are available year-round, but they have mating flights in the spring.

Egg-Laying behavior

Time of day: Afternoon

I had never read of this behavior before I saw it for myself. Boatmen climb out of the water in early spring (April where I watched them in northern Wisconsin) and are easily spotted on the remaining snow banks next to the river. The adults fly around over the river, sometimes quite high, and eventually splash down onto the surface, where they make a few kicks to break the film and then disappear. I presume this was their egg-laying behavior, and they did it in such numbers that trout probably fed well on them.

This is based on my one encounter, so there may be more variation in their behavior and I may have misread something.

Specimens of Water Boatmen:

3 Adults

7 Underwater Pictures of Water Boatmen:

1 Video of Water Boatmen:

Water Boatman Rowing

Water boatmen are excellent swimmers, and you can see here how they use their oars to push themselves through the water, a motion easily imitated by the fly fisher.


Start a Discussion of Corixidae

True Bug Family Corixidae (Water Boatmen)

Taxonomy
Genus in Corixidae
Sigara
1
3
Genus in Corixidae: Sigara
16 genera (Arctocorisa, Callicorixa, Cenocorixa, Centrocorisa, Corisella, Cymatia, Dasycorixa, Glaenocorisa, Graptocorixa, Hesperocorixa, Morphocorixa, Neocorixa, Palmacorixa, Pseudocorixa, Ramphocorixa, and Trichocorixa) aren't included.
Common Name
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