The Slate Drake

The Slate Drakes belong to the Isonychia genus of the Siphlonuridae family of
mayflies. The most important species is the
bicolor. It is a very common mayfly.
These mayflies are also called  “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. This makes it difficult to pin the exact times down.
When they do hatch, at times, it can be prolific. That's not often the case but
large hatches do occur in most trout streams that have good populations of

These mayflies crawl out of the water on the banks and on boulders and rocks
to hatch much like a stonefly. You will find their shucks along the banks after a

Hatches usually occurs late in the afternoon and sometimes on into the
evenings. It will sometimes occur during the day if it's very cloudy or rainy.
Some anglers claim that some Slate Drake mayflies hatch in the water but we
have never witnessed that and don't believe that its true. We do find a lot of
shucks where they obviously hatched out of the water. We have raised a few in
an aquarium and they too crawled up on rocks in the aquarium protruding out
of the water to hatch.
Copyright 2013 James Marsh
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