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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Little Gray Sedges
Like most common names,"Little Gray Sedge" can refer to more than one taxon. They're previewed below, along with 2 specimens. For more detail click through to the scientific names.
Caddisfly Genus Goera
These are often called Little Gray Sedges.
Caddisfly Genus Lepidostoma
These are very rarely called Little Gray Sedges.
This genus is important for trout anglers. Many species of Lepidostoma produce excellent hatches, especially in the West. Lepidostoma can be very prolific in spring creek environments or smaller runoff streams with springs. Lepidostoma togatum is the most important species of this genus in the East and Midwest. The West has several species that are important.
These specimens are still alive, just very cold, so the colors are accurate. I put them in the freezer for a bit to settle them down and overdid it a little:)
The photo of the specimen cased is alive. The photo of the uncased larva is the same specimen taken after it was preserved in its case. Unfortunately, there was a lot of pigment transfer making the specimen look olivaceous. In life it was grayish white as shown in the first photo.
See 7 more specimens...
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.