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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.

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 Species Nigronia serricornis (Fishflies)

This is an especially abundant dobsonfly species in my collections.

Where & when

In 98 records from GBIF, adults of this species have mostly been collected during June (32%), May (30%), July (20%), and April (13%).

In 26 records from GBIF, this species has been collected at elevations ranging from 295 to 5279 ft, with an average (median) of 1926 ft.

Specimens of the Hellgrammite Species Nigronia serricornis

1 Male Adult
4 Larvae

Start a Discussion of Nigronia serricornis


  • Brigham, W.U., A.K. Brigham, and A. Gnilke. 1982. Aquatic Insects and Oligochaetes of North and South Carolina. Midwest Aquatic Entomologist.
  • Knight, Allen W. and C.A. Siegfried. 1977. The Distribution of Corydalus cornutus (Linnaeus) and Nigronia serricornis (Say) (Megaloptera: Corydalidae) in Michigan. Great Lakes Entomologist 10(2): 39-46.
  • Neunzig, H.H. 1966. Larvae of the Genus Nigronia Banks. Proceedings of the Entomological Society of Washington 68(1): 11-16.
  • Stehr, Frederick W. 1998. Immature Insects. Kendall/Hunt Publishing Company.

Hellgrammite Species Nigronia serricornis (Fishflies)

  • NatureServe
  • Integrated Taxonomic Information System
  • Global Biodiversity Information Facility
  • Described by Say, T. Order Neuroptera. Pp. 303-310 in Keating, W. H. (ed.). Narrative of an expedition to the source of St. Peter's River, Lake Winnepeek, Lake of the Woods, &c. &c. performed in the year 1823, by order of the Hon. J. C. Calhoun, Secretary of War, under the command of Stephen H. Long, Major U.S.T.E. Vol. 2. Carey and Lea, Philadelphia. (1824).
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