The Black Mayfly Nymph is a traditional darker colored Mayfly nymph. This is a great nymph to add to your selection, fish can be very fussy and this is one of the few versatile black mayfly imitations that can bring a variety of species to the bank. These include: Rainbow Trout, Cut Throat Trout, Brown Trout, Lake Trout, Grayling, Whitefish, and Brook Trout. The Black Mayfly Nymph is a fantastic imitation for the autumn where the fish are looking for slightly larger prey than earlier in the year.