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

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 Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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.

Lateral view of a Isoperla (Perlodidae) (Stripetails and Yellow Stones) Stonefly Adult from Cayuta Creek in New York
Several stoneflies of this species were flying around a small stream last night. I tied on a brown drake imitation of about the right size/color to approximate these stones, and was rewarded with a hard-fighting 17-inch brown trout.
Posts: 2
Teamrenna on Jun 12, 2008June 12th, 2008, 8:19 am EDT
Edit: Post removed
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Jun 12, 2008June 12th, 2008, 3:25 pm EDT

Your comments confused me at first, until I realized that your perspective seems to be from a different part of the world. Neither Siphonoperla burmeisteri nor Xanthoperla apicalis is found in North America. (This specimen was collected from a small stream in New York, USA.)

...all Isoperla species are much bigger....

Perhaps that is true where you live, but some North American Isoperla are well within the size range indicated by the photo (+/-14mm from head to wingtips). As best I can sort it out, everything appears to be consistent with a perlodid ID. What structures do you see that suggest Chloroperlidae?
Posts: 2
Teamrenna on Sep 4, 2008September 4th, 2008, 9:00 am EDT
My bad Gonzo. I concluded to fast. Its of course a female Isoperla. I must have been blind or something when i posted my first comment.
Pay attention to the slight notch in this specimens subgenital plate (posterior, as seen in one of the pohots. What does your taxonomic keys say?
In my region (Norway),adult isoperla (grammatica, obscura and difformis) females can be separated by this feature.
This specimen has a difformis-like subgenital plate by the way.

Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Sep 9, 2008September 9th, 2008, 9:32 am EDT
My bad Gonzo.

Not a problem, Teamrenna. I always enjoy hearing from fly fishers and aquatic insect enthusiasts from other parts of the world. (And I dream of visiting your stunningly beautiful country some day!)

What does your taxonomic keys say?

I wish it were that easy. Unfortunately, if a comprehensive species-level key to all stages/sexes of North American Isoperla exists, I'm not aware of it. Many of the existing keys are either out of date or lead to a statement that says that females must be associated with males for identification. Part of the problem is that we have nearly 60 North American species assigned to this genus, and some adults are described mostly by distinctions in male genitalia. There are about 19 Isoperla species in my home state of Pennsylvania, with a few unnamed as yet.

In general appearance, this specimen looks much like Isoperla cotta. However, given the number of similar-looking species and the degree of variation among them, I still wouldn't hazard a guess about the species. Incomplete distribution records further compound our identification problems. For example, Isoperla cotta is not listed in the distribution records that I have seen for New York State, but I know that specimens identified and photographed by Dr. Whitney Cranshaw were collected there.

Lloyd (Gonzo)

Quick Reply

Related Discussions

Last Reply
Apr 13, 2007
by Troutnut
Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy