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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This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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Grannoms
This common name refers to only one genus. Click its scientific name to learn more.
Caddisfly Genus Brachycentrus
These are sometimes called Grannoms.
This prolific genus includes the popular eastern early-season Apple Caddis and Grannom hatches. Their life cycles are ideal for the fly angler, and every stage is frequent trout prey.
Note that this species changes color dramatically after it emerges, and imitations of egg-laying adults should be a different color from imitations of emergers. Emergers have pale blonde, almost off-white wings and bright green bodies, while the egg-laying adults have light brownish gray wings and medium green bodies.
Note that this species changes color dramatically after it emerges, and imitations of egg-laying adults should be a different color from imitations of emergers. Emergers have pale blonde, almost off-white wings and bright green bodies, while the egg-laying adults have light brownish gray wings and medium green bodies.
I captured this specimen in the same color as this photograph, during its egg-laying flight. The emergers are much lighter.
This species of Brachycentrus was extremely common in mid-September kick net samples in the Yakima canyon.
The green blob contained in this case is a pupa in the early stages of transformation from larva to the final stage we generally picture and imitate. This specimen and several like it were fixed to a rock I picked up, and each one had the front of its case sealed off, protecting the helpless pupa from predation. It's neat to see the insect part-way through such a radical transformation.
It was very hard to extract this thing from its case, so there's a bit of extra goo near the head from where I accidentally punctured it.
It was very hard to extract this thing from its case, so there's a bit of extra goo near the head from where I accidentally punctured it.
See 4 more specimens...
References
- Jacobus, L. M., Wiersema, N.A., and Webb, J.M. 2014. Identification of Far Northern and Western North American Mayfly Larvae (Insecta: Ephemeroptera), North of Mexico; Version 2. Joint Aquatic Science meeting, Portland, OR. Unpublished workshop manual. 1-176.
- Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.