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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 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.
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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Drunella flavilinea (Flav) Mayfly Nymph Pictures

Although the identification is not certain because the nymph is not yet mature, the configuration of tubercles on this one--particularly the forefemora--seems to best match Drunella flavilinea.

Drunella flavilinea (Ephemerellidae) (Flav) Mayfly Nymph from the Gallatin River in Montana
Dorsal view of a Drunella flavilinea (Ephemerellidae) (Flav) Mayfly Nymph from the Gallatin River in Montana
Ventral view of a Drunella flavilinea (Ephemerellidae) (Flav) Mayfly Nymph from the Gallatin River in Montana
Ruler view of a Drunella flavilinea (Ephemerellidae) (Flav) Mayfly Nymph from the Gallatin River in Montana The smallest ruler marks are 1 mm.
Lateral view of a Drunella flavilinea (Ephemerellidae) (Flav) Mayfly Nymph from the Gallatin River in Montana
Drunella flavilinea (Ephemerellidae) (Flav) Mayfly Nymph from the Gallatin River in Montana

This mayfly was collected from the Gallatin River in Montana on July 2nd, 2019 and added to Troutnut.com by Troutnut on July 18th, 2019.


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Drunella flavilinea (Flav) Mayfly Nymph Pictures

Collection details
Location: Gallatin River, Montana
Date: July 2nd, 2019
Added to site: July 18th, 2019
Author: Troutnut
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