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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.

Dorsal view of a Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
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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Hellgrammite Genus Corydalus (Dobsonflies)

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
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.

Where & when

In 181 records from GBIF, adults of this genus have mostly been collected during June (17%), July (17%), August (16%), May (14%), September (11%), and March (6%).

In 63 records from GBIF, this genus has been collected at elevations ranging from 10 to 8196 ft, with an average (median) of 3133 ft.

Specimens of the Hellgrammite Genus Corydalus

1 Larva

Discussions of Corydalus

Dobson Fly
26 replies
Posted by Jesse on Jun 23, 2011
Last reply on Sep 12, 2013 by PaulRoberts
What can anyone tell me about the Dobson Fly?

(General now guys, we don't have to go all scientific with it ha)!
Northern Delaware River - Hellgramite Goldmine
2 replies
Posted by Yemoss on May 29, 2007
Last reply on Jul 22, 2007 by GONZO
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.
Hellgrammite hell
1 replies
Posted by Sprattoo on Jun 5, 2007
Last reply on Jun 5, 2007 by Wiflyfisher
The First time I saw one of these things was as a kid. We were playing around a woolen mill in old Kezar Falls Maine.
Turning over a damp old pile of wool revealed a number of adult Hellgrammites. At the age of 12 or 13 these were the scariest things I had ever seen.... still very intimidating. I remember trying to get them to bite sticks and my shoe... which they happily did once I started poking them.

Now at the age of thirty *mumble mumble* This insect has come into my life again.
After opening my little tackleshop and selling flies and gear for about a year, it was an embarrassment that I couldn't catch the Browns surfacing all over the place down on the river.
I finally got one by accident, cut open its belly and found... thats right... A dobsonfly nymph.
Although I believe they were really feeding on dragonfly or damselfly nymphs (as they were chasing and feeding near the top)
The story of my trouts belly told a different tale.

Some time at the tying bench, with a few pieces of yarn and marabou and now those old browns are no problem at all!

Start a Discussion of Corydalus

References

  • Baumann, Richard W. 1975. Revision of the Stonefly Family Nemouridae (plecoptera) : a Study Of The World Fauna At The Generic Level. Smithsonian Contributions to Zoology undef(211): 1-74.
  • Brigham, W.U., A.K. Brigham, and A. Gnilke. 1982. Aquatic Insects and Oligochaetes of North and South Carolina. Midwest Aquatic Entomologist.
  • Stehr, Frederick W. 1998. Immature Insects. Kendall/Hunt Publishing Company.
  • Usinger, R.L. 1956. Aquatic Insects California, with keys to North American Genera and California species. University of California Press.

Hellgrammite Genus Corydalus (Dobsonflies)

Taxonomy
3 species (Corydalus cornutus, Corydalus lutea, and Corydalus texana) aren't included.
Common Name
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