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Great Western Leadwings

Scientific Name
MatchScientific Name
*Isonychia

This common name refers to only one genus.

Mayfly Genus Isonychia

These are very rarely called Great Western Leadwings.
Sporadic hatches are rarely as outstanding as those of Isonychia. On streams with good populations, they are reliably hatching in light numbers, here and there, for most of the evening through most of the mid- to late season.

The spinners, and occasionally the duns, produce more concentrated action, but the real value of the Isonychia hatch is its duration and the size of the flies; large trout become ever watchful for them, even when they aren't emerging.

All the species of Isonychia are similar in appearance and behavior.
Isonychia bicolor (Mahogany Dun) Mayfly NymphIsonychia bicolor (Mahogany Dun) Mayfly NymphView 7 PicturesThis Isonychia bicolor nymph from the Catskills displays the prominent white stripe sometimes characteristic of its species. This is the first such specimen I've photographed, because members of the same species in the Upper Midwest have a more subdued stripe (and were once thought to be a different species, Isonychia sadleri). The striking coloration on this eastern nymph is more appealing.
Region: Catskills
Collected Apr 19, 2006
Added Apr 21, 2006
Female Isonychia bicolor (Mahogany Dun) Mayfly DunFemale Isonychia bicolor (Mahogany Dun) Mayfly DunView 13 Pictures
Region: Upper Midwest
Collected Jun 14, 2005
Added May 26, 2006
Male Isonychia bicolor (Mahogany Dun) Mayfly SpinnerMale Isonychia bicolor (Mahogany Dun) Mayfly SpinnerView 15 PicturesI got several really nice pictures of this spinner. I also collected a female on the same trip.
Region: Northeast
Collected Aug 9, 2006
Added Aug 11, 2006
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Last update July 19th, 2007.
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