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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 Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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

References

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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