Isonychias are an iconic hatch on the Delaware System offering angling opportunities from May through October. Isonychias are strong swimmers that move quickly.  They also have the ability to crawl out and hatch on rocks or hatch in the river like many other mayflies.  They tend to hatch in the river in higher water conditions.  Long time Delaware Angler and fly collaborator Pat Giordano and I were looking for an Iso pattern that sat low in the water, floated well, and was visible.  We love the profile the floating nymph hook offers and the cdc / deer hair combo wing helped check off our other boxes.