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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GONZO on Apr 3, 2007April 3rd, 2007, 4:53 am EDT
From the anal gills and the markings, this appears to be Agnetina--probably capitata.
Boyle on May 7, 2007May 7th, 2007, 2:25 pm EDT
In case you didn't know, there is an excellent color drawing of Perla capitata, as the species was formerly known, which you can compare to your excellent color photographs. It serves as the frontispiece to Peter W. Claassen's Plecoptera Nymnphs of America North of Mexico (Springfield, Ill: The Thomas Say Foundation, 1931).On page 45 Claassen notes: "...easily recognized by the two dark transverse bands across the head, the two dark trabnsverse bands on the femeora, the presence of caudal gills and the yellow and dark banded abdomen." As with you, Claasssen was at Cornell.
Regards,
RH Boyle, Cooperstown, NY
Regards,
RH Boyle, Cooperstown, NY
Troutnut on May 8, 2007May 8th, 2007, 4:14 am EDT
Thanks Boyle, good info!
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Troutnut and salmonid ecologist
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