Hatches Made Easy:
Slate Drakes (Isonychia bicolor)
The Isonychia genus of the Siphlonuridae family of mayflies includes a species
named the bicolor that is a very common mayfly in the streams of the Great
Smoky Mountains National Park. These are also called “Slate Drakes”, “Dun
Variant”, “Leadwing Coachmans” and sometimes Mahogany Duns.
The species name, bicolor, comes from its legs that are bi-colored. The common
name “Leadwing” comes from the lead color of the flies’ wings. This mayfly can
hatch from spring until fall, but is very sporadic throughout that long period of
time and this makes it difficult to pin the exact time down. When they do hatch,
they usually cause the trout to feed.
Hatches usually occurs late in the afternoon and sometimes into the evenings
but will occur occasionally during the day if it is cloudy or rainy. This is an
unusual mayfly. Their behavior is similar to a stonefly. The nymphs crawl out
of the water to hatch, so imitating the dun is not productive.
Coming Up Next:
Slate Drake - Nymphs
Copyright 2008 James Marsh
Slate Drake Dun: Imitating the dun is not productive