Isonychia Dry

The Isonychia, also known as the Slate Drake or Mahogany Dun, is a classic dry fly designed to imitate the adult stage of Isonychia bicolor, a mayfly species often found in moderate to fast-moving waters. Known for its robust size and dark coloration, this fly is particularly effective during the late spring through fall months when these mayflies are most active.

Before fishing an ISO dry, lightly dull the hackle tips with a quick pinch between wet fingers—this knocks down the unnatural sheen just enough that the fly rides lower and leaves a softer footprint, which can make a big difference on slow water when trout are alert to glare and micro-drag.