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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.

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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Male Attenella attenuata (Small Eastern Blue-Winged Olive) Mayfly Dun Pictures

This specimen came from the same hatch as a female.

Lateral view of a Male Attenella attenuata (Ephemerellidae) (Blue-Winged Olive) Mayfly Dun from the Namekagon River in Wisconsin
Dorsal view of a Male Attenella attenuata (Ephemerellidae) (Blue-Winged Olive) Mayfly Dun from the Namekagon River in Wisconsin
Ventral view of a Male Attenella attenuata (Ephemerellidae) (Blue-Winged Olive) Mayfly Dun from the Namekagon River in Wisconsin

This mayfly was collected from the Namekagon River in Wisconsin on June 8th, 2005 and added to Troutnut.com by Troutnut on May 26th, 2006.

Discussions of this Dun

BWO
Posted by Oldredbarn on Jun 8, 2010
Last reply on Jun 8, 2010 by Oldredbarn
This third picture from the underside I find interesting. On my last trip to Au Sable in MI in late May 2010 I stopped to sit on some instream structure and was floored by the number of nymphs crawling around on my wading boots. There is always something there but this particular time the activity was heavy.

One of the nymphs stuck out from the others and had this same greenish color as this dun. All the others seemed very dark, the typical browns to black.

I was in fairly fast water that was hip deep in spots and maybe deeper towards the middle of the stream...Anyway it caught my eye and I should of hung on to it or took a photo.

It was very warm up there for that time in May...

One of the nights a friend and I were trying to figure out what was going on. I stepped out in to the bubble stream with a small siene and again was floored about the number of bugs being caught in it. I think it may have been one of those "benthic drift" situations we have all read about...There was everything in large numbers but very small stuff and for the most part mangled up...Or so it seemed...

These may have been smallish spinners, but no feeding fish interested...It was frustrating to say the least...I was showing primo water to someone who had never been there before...I was trying to show it off and the fish were snubbing their noses at us...I guess they weren't even doing that really...They were probably stuffing themselves underwater on all the activity...

Just obsevations here.

Spence

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Male Attenella attenuata (Small Eastern Blue-Winged Olive) Mayfly Dun Pictures

Collection details
Location: Namekagon River, Wisconsin
Date: June 8th, 2005
Added to site: May 26th, 2006
Author: Troutnut
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