Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin

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.

Stream photos

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Grammotaulius betteni (Northern Caddisfly) Caddisfly Larva Grammotaulius betteni (Northern Caddisfly) Caddisfly Larva

Dorsal view of a Grammotaulius betteni (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington

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.

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27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.

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Northern Delaware River - Hellgramite Goldmine

This topic is about the Hellgrammite Genus Corydalus

The largest and most well-known hellgrammites belong to this genus, although in my collecting experiences the fishflies of Nigronia seem to be more common in trout streams.

Example specimen

27
Corydalus (Dobsonfly) Hellgrammite Larva

Large hellgrammite (dobsonfly larva). This nearly two inch long larva from the genus Corydalus is a fearsome predator

Dorsal view of a Corydalus (Corydalidae) (Dobsonfly) Hellgrammite Larva from Paradise Creek in Pennsylvania

Yemoss
Posts: 1

Yemoss on May 29, 2007May 29th, 2007, 6:02 pm EDT

Far from a fly-fisherman, I still wanted to identify a menacing- looking insect which invaded our late-night campfire council this past Memorial Day Weekend in Millford, PA on the Delaware River (cr 206 n). We stayed at Kittatiny Canoe Campgrounds, very commercial, but made the best of it. The amount of these bugs crawling around at night, lured by our glowing fire, was incredible. Today I identified them as Hellgramites, and also learned that they are prized by bass and trout. Didn't even think to bring a pole with the short weekend - we went rafting instead. Still wanted to inform fellow fisherman of the abundance and location of this critter. Important to note that our sites bordered the river - one website I read indicated that Hellgramites won't go more than 50 yards inland from their water source; I'm not sure if that's common to most aquatic species but I'd imagine so.

Wbranch

York & Starlight PA

Posts: 2635

Wbranch on Jul 22, 2007July 22nd, 2007, 4:04 am EDT

I think the adult, winged insect, is called a Dobson Fly. They seem attracted to light and fly around in the night and can scare the heck out of you as they have big wings and pincers.

Catskill fly fisher for fifty-five years.

GONZO
Site Editor
"Bear Swamp," PA

Posts: 1681

GONZO on Jul 22, 2007July 22nd, 2007, 4:21 am EDT

...one website I read said that Hellgrammites won't go more than 50 yards inland from their water source....

Yemoss, that may have been referring to the travels of the Dobsonfly larvae (hellgrammites); they pupate terrestrially. Many adult aquatic insects are attracted to lights, often quite some distance from stream or lake.