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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Stonefly Genus Leuctra (Needleflies)
Ernest Schwiebert notes in Matching the Hatch that trout are very fond of these uncommon stoneflies when they are available.
Genus Range
Start a Discussion of Leuctra
References
- Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.
- Schwiebert, Ernest G. 1955. Matching the Hatch. MacMillan Publishing Company.
Stonefly Genus Leuctra (Needleflies)
Taxonomy
Species in Leuctra
Leuctra carolinensisCarolina Needleflies
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Leuctra duplicataAtlantic Needleflies
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Leuctra ferrugineaEastern Needleflies
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Leuctra mariaNortheastern Needleflies
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Leuctra mohaBlackwater Needleflies
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Leuctra sibleyiBrook Needleflies
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Leuctra tenellaBroad-lobed Needleflies
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Leuctra trilobaThree-lobed Needleflies
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Leuctra variabilisVariable Needleflies
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Species in Leuctra: Leuctra carolinensis, Leuctra duplicata, Leuctra ferruginea, Leuctra maria, Leuctra moha, Leuctra sibleyi, Leuctra tenella, Leuctra triloba, Leuctra variabilis
17 species (Leuctra alabama, Leuctra alexanderi, Leuctra alta, Leuctra baddecka, Leuctra biloba, Leuctra cottaquilla, Leuctra crossi, Leuctra grandis, Leuctra laura, Leuctra mitchellensis, Leuctra monticola, Leuctra nephophila, Leuctra paleo, Leuctra rickeri, Leuctra szczytkoi, Leuctra tenius, and Leuctra truncata) aren't included.