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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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MItroutbum
Posts: 3
MItroutbum on Jun 13, 2008June 13th, 2008, 3:44 am EDT
Hey guys, I am new to the forum, and as of this past October, a new resident to the state of Michigan. I have fished extensively in the SE and learned alot of the insects down there, but now that I am up here I have been seriously confused my the naming of many of the larger mayflies (I am mostly a rookie with insects if you cant tell!)

So......
The one thing thats confusing are what people up here refer to as Iso's. I have seen some reference to these as Slate Drakes and they appear slate gray, where others refer to them as Mahogony Duns and they are a dark brown color. Can anyone explain?? What size and color are the Iso's that I should tie up for the upcoming hatches??


Quillgordon
Schuylkill County, PA.

Posts: 109
Quillgordon on Jun 13, 2008June 13th, 2008, 4:15 am EDT
From this website...... if you missed it!
http://www.troutnut.com/hatch/93/Mayfly-Isonychiidae-Slate-Drakes


Patterns ...........
http://flyfishingconnection.com/patterns/flies/51/Isonychia+nymph
http://flyfishingconnection.com/patterns/flies/295/Isonychia+CDC+Emerger
Cheers....
Flyfishing is a state of mind! .............. Q.g.

C/R........barbless
Freepow
menomonie, WI

Posts: 83
Freepow on Jun 13, 2008June 13th, 2008, 4:17 am EDT
What part of Michigan are you in?
"I fish...because I suspect that men are going along this way for the last time, and I for one don't want to waste the trip..."
MItroutbum
Posts: 3
MItroutbum on Jun 13, 2008June 13th, 2008, 5:44 am EDT
Hmmmm, so the Iso body is a Mahogony type color with slate or dark dun colored wings??

I am living in Grand Rapids and loving it so far, we just got back from the UP and had a great time catching lots of beautiful fish.

Rich
Freepow
menomonie, WI

Posts: 83
Freepow on Jun 13, 2008June 13th, 2008, 8:59 am EDT
Both beautiful parts of Michigan. I grew up in the UP and spent quite a bit of time in Grand Rapids. I never got to fish downstate but I sure enjoy fishing in the UP.
"I fish...because I suspect that men are going along this way for the last time, and I for one don't want to waste the trip..."
Wiflyfisher
Wiflyfisher's profile picture
Wisconsin

Posts: 622
Wiflyfisher on Jun 14, 2008June 14th, 2008, 3:11 pm EDT
Hmmmm, so the Iso body is a Mahogony type color with slate or dark dun colored wings??


Yes, see...

http://www.troutnut.com/hatch/93/Mayfly-Isonychiidae-Slate-Drakes
http://www.wiflyfisher.com/isonychia-bicolor-mayfly-hatch.asp


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