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 Clark's Fork of the Yellowstone River in Wyoming

Stream photos

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Setvena wahkeena (Wahkeena Springfly) Stonefly Nymph Setvena wahkeena (Wahkeena Springfly) Stonefly Nymph

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.

7 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.

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.

Can't wait to hit this hatch

This topic is about the Mayfly Species Baetisca laurentina

This Midwestern species is responsible for all my Baetisca fishing experiences. Read the section on the genus Baetisca for most of the details.

Example specimens

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Female Baetisca laurentina (Armored Mayfly) Mayfly Spinner

Lateral view of a Female Baetisca laurentina (Baetiscidae) (Armored Mayfly) Mayfly Spinner from the Bois Brule River in Wisconsin

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Female Baetisca laurentina (Armored Mayfly) Mayfly Dun

Artistic view of a Female Baetisca laurentina (Baetiscidae) (Armored Mayfly) Mayfly Dun from the Marengo River in Wisconsin

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Baetisca laurentina (Armored Mayfly) Mayfly Nymph

The angle of this picture shows the characteristic frontal process of B. laurentina: it is well developed but does not extend beyond the anterior margin of the head. In the angle most convenient, and the angle of most of the top-view pictures above, it looks like it extends beyond the head. The angle of this picture tells the truth.

Baetisca laurentina (Baetiscidae) (Armored Mayfly) Mayfly Nymph from unknown in Wisconsin

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Jun 12, 2006June 12th, 2006, 11:59 am EDT

It sounds like the Baetisca hatch is really going on here in northern Wisconsin now. I've heard reports from more than one source about fishable Baetisca laurentina hatches on two of my favorite rivers. I bought some imitations and hopefully I'll be using them tomorrow!

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist