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.
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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.
- 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.
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Aafloyd on Oct 31, 2011October 31st, 2011, 7:03 pm EDT
I realize this is well worn topic on the forum, but I just got through posting a comment stating that I had Hexagenia limbata alongside Anthopotamus distinctus here in Southwest Virginia. After posting it I second guessed... and in reading the discussions on the forum about this there seems to be some hent that a broad geographical division line can be drawn between Hexagenia rigida and Hexagenia limbata with limbata being more common in the northern midwest and rigida being more common in east/southeast with a ton of overlap. So my question is: if this is true and would being in SW Virginia (near NC) increase the likely hood of one over the other?
I'll post a photo of the specimen shortly,
aaron
I'll post a photo of the specimen shortly,
aaron
Taxon on Oct 31, 2011October 31st, 2011, 7:35 pm EDT
Aaron-
Will be interested to see your photo. However, unless it clearly shows the penes of a male imago, attempting to differentiate between Hexagenia limbata and H. rigida would be highly speculative, at least in my opinion.
Will be interested to see your photo. However, unless it clearly shows the penes of a male imago, attempting to differentiate between Hexagenia limbata and H. rigida would be highly speculative, at least in my opinion.
Aafloyd on Oct 31, 2011October 31st, 2011, 7:38 pm EDT
Next year I'm photographing the penes! Perhaps it is better to attempt to resolve it after that - in the meantime I'll just refer to them as the Hexes of late June.
Oldredbarn on Nov 1, 2011November 1st, 2011, 5:49 am EDT
Next year I'm photographing the penes!
Aaron...Don't say that too loudly, your neighbors will be putting you on the list...:)
That is a wonderful photo, by-the-way...Somewhere on here I have some pictures of her cousin, step-child maybe more correct since she's been moved from the genus...Still hasn't been totally kicked out of the family yet, but who knows...Litobrancha recurvata.
Spence
You add anymore drakes to your posts and we all may be paying you a visit next summer!
"Even when my best efforts fail it's a satisfying challenge, and that, after all, is the essence of fly fishing." -Chauncy Lively
"Envy not the man who lives beside the river, but the man the river flows through." Joseph T Heywood
"Envy not the man who lives beside the river, but the man the river flows through." Joseph T Heywood
Jmd123 on Nov 2, 2011November 2nd, 2011, 8:05 am EDT
These mayfly photos are killing me...what I wouldn't do for a good hatch right now...
Jonathon
Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
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by Troutnut
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