Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin

Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Stream photos

Featured on the forum

Re: Trico emergers
In the Mayfly Genus Tricorythodes by Bwoklink (Martinlf replied)

Re: Trico Tips
In the Mayfly Genus Tricorythodes by Martinlf

Re: UV spectrum and trout
In General Discussion by Martinlf

Re: closing the gender gap in flyfishing
In General Discussion by Konchu (Smallflyguy replied)

Re: Fishing Kupa River, Slovenia
In Fishing Reports by Slocum (Fish1 replied)

Grammotaulius betteni (Northern Caddisfly) Caddisfly Larva Grammotaulius betteni (Northern Caddisfly) Caddisfly Larva

Dorsal view of a Grammotaulius betteni (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington

This is a striking caddis larva with an interesting color pattern on the head. Here are some characteristics I was able to see under the microscope, but could not easily expose for a picture:
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.

12 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.

Baetis tricaudatus (Blue-Winged Olive) Mayfly Nymph Pictures

Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

Ruler view of a Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington The smallest ruler marks are 1 mm.

Ventral view of a Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

Dorsal view of a Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

There serrations of the gills that are supposed to characterize this species are maaaaybe visible on the sharpest edge of the gill in the middle, but I might just be imagining things. Crystal-clear images of the serrations are shown in a scientific paper using an electron microscope at about 2200x magnification, so I don't know if they're even visible under a dissecting microscope at all.

Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

Mouth parts, ventral view, with the labium removed

Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

View of the labium removed from the rest of the head, since the shape of the labial palp is an important identifying characteristic

Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

I took this picture to capture the markings on the pronotum, after I had removed the head to dissect mouthparts.

Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

There were some short, stout setae on the pedicels, a key characteristic, but I couldn't get a sharp enough photo for you to see them.

Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the South Fork Snoqualmie River in Washington

This mayfly was collected from the South Fork Snoqualmie River in Washington on May 14th, 2022 and added to Troutnut.com by Troutnut on May 16th, 2022.

Start a Discussion of Nymph

References

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.