Fly Tying a Micro Nymph with Catgut Biothread

Prior to tying, soak the part of Catgut Biothread that you want to use in warm water for 3-5 minutes. The color will change from opaque to more milky and transparent and the material will be super-flexible and easy to wrap. When the fly dries, the body will go back to its solid-colored state.

By using various colored threads for underbody, different effects can be achieved as the color peaks through the wet material. The combinations are really limitless.