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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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Lateral view of a Male Hexagenia limbata (Ephemeridae) (Hex) Mayfly Spinner from Atkins Lake in Wisconsin
Daleeahrens
winneconne

Posts: 1
Daleeahrens on Jun 16, 2016June 16th, 2016, 7:58 am EDT
in my area, central wisc, the hex hatch has just started, although i havent seen a one, this is my first yr fishing the hex. any help what so ever would be gratly appreciated, thanx, standing by
Wiflyfisher
Wiflyfisher's profile picture
Wisconsin

Posts: 622
Wiflyfisher on Jun 17, 2016June 17th, 2016, 4:45 am EDT
in my area, central wisc, the hex hatch has just started, although i havent seen a one, this is my first yr fishing the hex. any help what so ever would be gratly appreciated, thanx, standing by

Hexs burrow in the slow silty/mucky bottom areas. The hatch generally doesn't start until dark and can go into the late night hours. When I have fished the hex hatch I don't even go down to the river until dusk and sit and wait for the hatch to begin. Sometimes I wait and nada and other times it bursts into clouds of flying insects that sounds like little birds flying all around you in the dark along with loud gulping sounds of big fish gorging themselves. I have also witnessed it on lakes and it seems like every fish in the lake, is gorging themselves on Hex nymphs and emerging duns, even walleye.
Wbranch
Wbranch's profile picture
York & Starlight PA

Posts: 2635
Wbranch on Jun 17, 2016June 17th, 2016, 7:35 pm EDT
Talking about every fish eating mayflies when there is a huge emergence. On the Susquehanna River in PA around Wrightsville and Columbia the white fly emerges from early to late July. It has an interesting adult life in that it changes from dun to spinner virtually right in front of your eyes. The duns start to emerge at dusk and there are millions of them. They land all over you and if you are wigged out by bugs crawling over you don't stay on the river as dark is approaching. I button my collar button and put in ear plugs to keep them out of my ears. If you observe the dun closely you will see in very short order the body starts to quiver and it starts to transform from dun to spinner. The dun skin splits and the spinner crawls out of the shuck and the shuck does not disengage but stays attached to the spinner.

Besides the smallmouth bass rising with abandon the channel catfish come into the shallows and just hold position in very shallow water with their mouths open and keep sucking in the spinners. I've also seen crayfish in the shallows with their claws sticking out of the water so they can grab a spinner as it floats by.
Catskill fly fisher for fifty-five years.
Wiflyfisher
Wiflyfisher's profile picture
Wisconsin

Posts: 622
Wiflyfisher on Jun 18, 2016June 18th, 2016, 5:00 am EDT
It has an interesting adult life in that it changes from dun to spinner virtually right in front of your eyes.

Matt, are you thinking of Ephoron luekon? Hexagenia limbata spinners return to the water 1-3 days after their emergence.
TNEAL
GRAYLING. MICHIGAN

Posts: 278
TNEAL on Jun 19, 2016June 19th, 2016, 7:36 am EDT
If you don't like fishing at night, most rivers have daytime emergences of hex flies . It may not be heavy, but the fishing is excellent; taking fish in the 20" plus range is not uncommon. Most are locked in to the night time stuff, so there's far less traffic in the daylight hours. I use a smaller fly; generally a #10 3xl for daytime hex fishing. If anyone wants the pattern, message me.
Wbranch
Wbranch's profile picture
York & Starlight PA

Posts: 2635
Wbranch on Jun 20, 2016June 20th, 2016, 5:13 pm EDT
Matt, are you thinking of Ephoron luekon? Hexagenia limbata spinners return to the water 1-3 days after their emergence


Yes. Over the past few days there has been an epic emergence of a very large, #8, mayfly on the Susquehanna. I don't know what it is as I've only seen the spinners on the ground under the lights at gas stations.

The body is about 1.25" long and about 3/16" in diameter. The color of the abdomen and thorax is a tannish yellow and there are some brown markings on the dorsal side of the body. Any ideas as to what it is?

I thought I might get to fish to the duns last night and stayed until 9:20 but never saw a single dun.

BTW the wings of the spinner are much clearer than those of the Hexagenia limbata spinner on the Troutnut page. No brown tinge at all.
Catskill fly fisher for fifty-five years.
TNEAL
GRAYLING. MICHIGAN

Posts: 278
TNEAL on Jun 21, 2016June 21st, 2016, 10:43 am EDT
that size and color combo sounds like hexagenia... very similar to our big flies in MI
Wiflyfisher
Wiflyfisher's profile picture
Wisconsin

Posts: 622
Wiflyfisher on Jun 22, 2016June 22nd, 2016, 2:48 pm EDT
Matt, are you thinking of Ephoron luekon? Hexagenia limbata spinners return to the water 1-3 days after their emergence


The body is about 1.25" long and about 3/16" in diameter. The color of the abdomen and thorax is a tannish yellow and there are some brown markings on the dorsal side of the body. Any ideas as to what it is?

I thought I might get to fish to the duns last night and stayed until 9:20 but never saw a single dun.

BTW the wings of the spinner are much clearer than those of the Hexagenia limbata spinner on the Troutnut page. No brown tinge at all.

Matt, see my page here... http://www.wiflyfisher.com/hex-limbata-mayfly-hatch.asp. Does that look more like what you saw?
Jmd123
Jmd123's profile picture
Oscoda, MI

Posts: 2474
Jmd123 on Jun 22, 2016June 22nd, 2016, 3:17 pm EDT
Anybody here in MI see any Hex yet?? It should be any day now, yesterday I saw a few big flies on the front steps of my college...Brown Drakes hatched around here about 2 weeks ago. I don't have Hex in my trout waters, but those Cooke Pond smallies just love 'em!

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
TimCat
TimCat's profile picture
Alanson, MI

Posts: 121
TimCat on Jun 23, 2016June 23rd, 2016, 9:40 pm EDT
I know the hex hatch is famous for the emergence at night, but how is the nymphing during the day? TNEAL mentioned a smaller hatch during the day which is nice to look for, but anybody have any experiences nymphing during the later part of the day before a "classic" hex hatch that evening? Do they emerge from the silt-dwelling nymph to dun pretty quickly? I'm curious.
"If I'm not going to catch anything, then I 'd rather not catch anything on flies" - Bob Lawless
Jmd123
Jmd123's profile picture
Oscoda, MI

Posts: 2474
Jmd123 on Jun 24, 2016June 24th, 2016, 9:32 am EDT
The Hex hatch is ON!! Big fat Cooke Pond smallies were taking them, along with Brown Drakes and Light Cahills. The summer hatch season is now in full swing!

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...

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