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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Report at a Glance
| Time of Day | 1500-2100 |
| Fish Caught | One smallmouth bass, One rainbow trout |
| Conditions & Hatches | Falling Clear water in the upper 50's Flow was approx 700cfs Mostly sunny skies Very breezy untill the sun started to drop March Brown/Grey Foxes Dorthea Assorted Caddis (most prominent were tan/tan and tan/green) |
Details and Discussion
JOHNW on May 15, 2008May 15th, 2008, 4:35 pm EDT
Nymphed hard for the first 4 hours and only resulted in the lone smalmouth. Wind made upstream cast very difficult and flow required 5-8 BB shot to get to the bottom (on top of heavily weighted nymphs).
Mayflies started to get going around 1900 and the frustration began. This wasn't the typical frustration of not being able to get fish to take but instead seeing so many bugs on the water and absolutly nothing working them. Finally around 2015 a few fish started to roll on some duns and I was able to hook and land a very fat and fiest bow before losing light to wade by.
Overall a beautiful but very disappointing day.
Forecast is for rain and an east wind on the Raritan bay tomorrow hopefully the rockfish will be cooperative.
John
Mayflies started to get going around 1900 and the frustration began. This wasn't the typical frustration of not being able to get fish to take but instead seeing so many bugs on the water and absolutly nothing working them. Finally around 2015 a few fish started to roll on some duns and I was able to hook and land a very fat and fiest bow before losing light to wade by.
Overall a beautiful but very disappointing day.
Forecast is for rain and an east wind on the Raritan bay tomorrow hopefully the rockfish will be cooperative.
John
"old habits are hard to kill once you have gray in your beard" -Old Red Barn
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