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.

Neversink Gorge (Wolf Brook) in New York

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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Female Hesperoperla pacifica (Golden Stone) Stonefly Adult Pictures

I collected this specimen as a nymph and had it in line to be photographed, but it emerged inside my holding container before I got the chance. However, I was able to get some interesting photos of the very freshly-emerged adult that really demonstrate how strikingly colors can change within a few short hours after emergence. The before-and-after pictures are combined here under a single specimen since they portray the same individual at different times within the same stage.

Based on the identification of another specimen from the same date/site, I'm calling this Hesperoperla pacifica.

Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana

Lateral view of a Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana

Ruler view of a Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana The smallest ruler marks are 1 mm.

Ventral view of a Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana

This stonefly was collected from the Gallatin River in Montana on July 2nd, 2019 and added to Troutnut.com by Troutnut on July 18th, 2019.

Start a Discussion of Adult

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.