Header image
Enter a name
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 Sweltsa (Chloroperlidae) (Sallfly) Stonefly Nymph from the Yakima River in Washington
This species was fairly abundant in a February sample of the upper Yakima.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Female Isoperla fusca (Yellow Sally) Stonefly Adult Pictures

The family ID on this one was a little bit tricky. Just going by the size, shape, and color, it looks like Chloroperlidae. However, the second anal vein of the forewing is does not appear to be forked, and the apical maxillary palpal segment is close to the length of the penultimate segment, both of which rule out that family. The position of the cubitoanal crossvein relative to the anal cell in the forewing -- touching it in this case -- indicates Perlidae (and it really doesn't have the "look" of Perlidae at all), but other characteristics, such as the metathorastic sternacostal sutures and lack of gill remnants, point to Perlodidae. That's the right answer. Moving on to Perlodidae, the key characteristics in Merritt & Cummins lead straightforwarly to Isoperla, and the species key in Jewett 1959 (The Stoneflies of the Pacific Northwest) leads to Isoperla fusca.

There is one caveat: That source does suggest a May-July emergence, whereas this one was collected in mid-September.

Ruler view of a Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington The smallest ruler marks are 1 mm.
Lateral view of a Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Ventral view of a Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Dorsal view of a Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Mesobasisternum

Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Metabasisternum, backlit

Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Metabasisternum, toplit

Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington
Female terminalia, backlit

Female Isoperla fusca (Perlodidae) (Yellow Sally) Stonefly Adult from the Yakima River in Washington

This stonefly was collected from the Yakima River in Washington on September 17th, 2020 and added to Troutnut.com by Troutnut on September 19th, 2020.

Discussions of this Adult

Stuck on the family ID on this one -- any thoughts?
Posted by Troutnut on Sep 19, 2020
Last reply on Sep 19, 2020 by Troutnut
See the caption to this specimen for the reasons why I'm not sure what family to place it in. In a nutshell, it looks like Chloroperlidae, seems to key to Perlidae, and doesn't look like Perlidae at all. I'm either missing or misinterpreting some key features or stumbled upon a specimen that violates a bunch of "usually" characteristics in the key.

Start a Discussion of Adult

Female Isoperla fusca (Yellow Sally) Stonefly Adult Pictures

Collection details
Location: Yakima River, Washington
Date: September 17th, 2020
Added to site: September 19th, 2020
Author: Troutnut
Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy