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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This was the only Rhithrogena specimen in a large sample of nymphs from a small Catskill stream. It looks virtually identical to Rhithrogena impersonata specimens collected in the Midwest, but I didn't get to check the distinguishing features under a microscope.
Kinza
Posts: 1
Posts: 1
Kinza on Feb 4, 2017February 4th, 2017, 3:31 am EST
Can you please identify the genus of Family Heptagenedae if I send you images?
Millcreek on Feb 4, 2017February 4th, 2017, 4:17 am EST
Kinza-
Possibly, if the photos are good and show distinguishing characteristics.
Possibly, if the photos are good and show distinguishing characteristics.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
-Albert Einstein
Crepuscular on Feb 6, 2017February 6th, 2017, 3:06 am EST
Are you sending adult or immature specimen photos?
General location is somewhat helpful as well. I'm assuming North America here, so NW, SW,MW,NE,SE.
If you are sending photos of the nymphs, the following is helpful (necessary for a confident identification):
1.a good ventral photo of the abdomen
2. A good dorsal photo of the abdomen with gills plainly visible
3.A good photo of the terminal abdominal segment with caudal filaments visible
4.A good Dorsal photo of the head
5.Fairly detailed photos of gills on segments 1-6.
General location is somewhat helpful as well. I'm assuming North America here, so NW, SW,MW,NE,SE.
If you are sending photos of the nymphs, the following is helpful (necessary for a confident identification):
1.a good ventral photo of the abdomen
2. A good dorsal photo of the abdomen with gills plainly visible
3.A good photo of the terminal abdominal segment with caudal filaments visible
4.A good Dorsal photo of the head
5.Fairly detailed photos of gills on segments 1-6.
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