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 Perlesta (Golden Stones)
This is a large genus in the Acroneuriinae subfamily that currently contains 24 species. Distribution is primarily southern though a few species make it into the East and Midwest. Perlesta placida is reportedly a common species. Only a single western species of limited importance and distribution is known for the southern Rockies.
Genus Range
Identification
To determine whether a specimen of Perlidae belongs to Perlesta, use the Key to Genera of Perlidae Nymphs.
Specimens of the Stonefly Genus Perlesta
1 Female Adult
This stonefly species was the most common insect over the small stream I fished one August afternoon; I saw dozens in their egg-laying flights.
Discussions of Perlesta
Perlesta placida
14 replies
Posted by Mad4Trout on Jul 3, 2011 in the species Perlesta placida
Last reply on Nov 27, 2011 by Mad4Trout
I don't know why "Stoneflies of the United States" has such a limited range for Perlesta placida, but we (Madmen Chapter of TU) have collected them on the Mad River, Logan Co., OH. They were reported by Gaufin (1956, Ohio J. Sci. 56 (6):321-324) in numerous counties. They have been recorded more recently by Ohio EPA.
Start a Discussion of Perlesta
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.
Stonefly Genus Perlesta (Golden Stones)
Taxonomy
Species in Perlesta
Perlesta adenaAdena Stone
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Perlesta baumanniDarkwing Stone
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Perlesta browniToothed Stone
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Perlesta cinctipesPlains Stone
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Perlesta decipiensWidespread Stone
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Perlesta lagoiGulf Stone
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Perlesta placidaFreckled Stoneflies
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Perlesta xubePawnee Stone
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Species in Perlesta: Perlesta adena, Perlesta baumanni, Perlesta browni, Perlesta cinctipes, Perlesta decipiens, Perlesta lagoi, Perlesta placida, Perlesta xube
10 species (Perlesta bolukta, Perlesta dakota, Perlesta etneri, Perlesta frisoni, Perlesta fusca, Perlesta golconda, Perlesta nelsoni, Perlesta nitida, Perlesta shubuta, and Perlesta teaysia) aren't included.