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.

The trees were leafing out and the trout were rising on this productive Wisconsin stream

From the Namekagon River in Wisconsin

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 Pictetiella expansa (Autumn Springfly) Stonefly Adult Pictures

Based on photos, this specimen seems to key out (using Merritt & Cummins 4th Edition) to Pictetiella expansa, but some of the characteristics aren't 100 % clear. Frisonia picticeps is another possibility. The range map doesn't show Pictetiella expansa in Washington, but that species is listed elsewhere as occurring near Puget Sound, and the head markings are similar to (albeit not a perfect match for) those of a male from Colorado in the scientific literature.

Lateral view of a Female Pictetiella expansa (Perlodidae) (Autumn Springfly) Stonefly Adult from the South Fork Snoqualmie River in Washington

Female Pictetiella expansa (Perlodidae) (Autumn Springfly) Stonefly Adult from the South Fork Snoqualmie River in Washington

Ventral view of a Female Pictetiella expansa (Perlodidae) (Autumn Springfly) Stonefly Adult from the South Fork Snoqualmie River in Washington

Ruler view of a Female Pictetiella expansa (Perlodidae) (Autumn Springfly) Stonefly Adult from the South Fork Snoqualmie River in Washington The smallest ruler marks are 1/16".

Dorsal view of a Female Pictetiella expansa (Perlodidae) (Autumn Springfly) Stonefly Adult from the South Fork Snoqualmie River in Washington

This stonefly was collected from the South Fork Snoqualmie River in Washington on June 16th, 2018 and added to Troutnut.com by Troutnut on July 3rd, 2018.

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.