This common name refers to only one genus.
These are sometimes called 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 Nymph
View 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.
Collected April 19, 2006
from in Added to Troutnut.com by on April 21, 2006