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.

Two major forks of this grayling stream come together in this pretty pool.

From the Chena River in Alaska

Stream photos

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Ephemerella mucronata Mayfly Nymph Ephemerella mucronata Mayfly Nymph

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington

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.

17 Recently Added Photos

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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Isoperla quinquepunctata (Little Yellow Stonefly) Stonefly Nymph Pictures

Size - (excluding tails) - 10 mm
Status at time of photo - preserved but no discernible color change as specimen was captured only a few days earlier.
Key characters - unique pattern on dorsal head and thorax; dark medial terga stripe between two paler stripes

This species is very common in west slope north Sierra watersheds. Richard W. Baumann & Boris C. Kondratieff did a study on the same section and at the same time of year (APRIL 25-29, 2010) where this specimen was taken. No other species of Isoperla were reported from this location and quinquepunctata was very abundant. Their hatches can be very heavy some Springs.

Entoman

This stonefly was collected from the Lower Yuba River in California on March 21st, 2011 and added to Troutnut.com by Entoman on November 1st, 2011.

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References

Allen RK. 1977. New species of Ephemerella (Ephemerella) from Alberta (Ephemeroptera: Ephemerellidae). The Pan-Pacific Entomologist 53: 286-286.
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.