O'Brien Outdoors: The Slate Drake

A very common mayfly that appears on most area streams is the slate drake Genus: Isonychia (pronounced i-son-ick-e-uh). Entomologists tell us that of the two most common species - bicolor and sadleri, the former is most prevalent in the East.

The slate drake (bicolor) gets its name from its bi-colored legs: light cream-colored mid and rear legs, brown front legs. The slate drake has two generations per year; typically a larger fly (size 10-12) emerges in May and June, and a smaller version (size 12-14) shows up in September and October, although this can vary from one stream to the next. Sporadic hatching can also take place throughout the summer, especially on cooler days.

Slate drake nymphs are streamlined and are fast, agile swimmers, exhibiting explosive bursts. This trait can be duplicated with short, quick line strips. They are abundant on freestone and limestone streams, with the best populations found in faster stream sections. The nymphs are easily identifiable with their pale dorsal stripe against a brown to black body. Gill tufts are evident at the base of the legs on the underside of the thorax.

The bicolor nymphs migrate to stream shallows in anticipation of emerging. They then climb out of the water on exposed rocks or logs. The empty nymphal shucks found along the water’s edge are evidence of a recent emergence. Trout take advantage of this movement and will feed in quite shallow water if undisturbed. A stealthy approach and delicate presentation can be quite effective. A few of the patterns with a proven track record include Zug Bug, Prince Nymph, and Kemp Bug. I have also found a Lead Wing Coachman tied with a reduced wing to work quite well. The reoccurring theme on these flies is the peacock herl body; the iridescence a good duplicate to the naturals’ coloration.

The freshly hatched duns are dark reddish to brown in body color with opaque, smoke-colored wings. Again, the middle and rear legs will be a cream to yellow, and the front legs dark brown. Heaviest concentrations of insects come early or late in the season. In between, activity is mostly sporadic. Even though this mayfly emerges from its nymphal shuck out of water, apparently enough find their way to the trout’s dinner plate to warrant fishing a dry fly.

Although typically short in duration, the concentrated spinner falls of the slate drake provide excellent angling opportunities, even late in the season. The body is reddish-brown and the transparent wings have a definite sparkle. The brown front legs have white feet and are often held up as if in a hand-shake gesture. This so-called communication and the white feet gave way to the name white-gloved howdy, a common name used by fly fishermen when referring to the spinner stage of the slate drake. Look for spinner activity near dusk (late afternoon in the fall of the year) with the heaviest concentrations of mating flights over the riffles. The well-prepared angler will carry both hackled and flush-floating patterns to meet the trout’s preference.     

The slate drake can be found in some numbers on most north central Pennsylvania streams, but heavy populations exist on Big Pine Creek, Little Pine Creek, Loyalsock Creek, and Penns Creek.               

Look for those telltale nymphal shucks on streamside rocks and be stocked with imitations of both the immature and mature stages of the slate drake. It can provide wonderful fishing for months to come.

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