Yes, I actually have a portable fly-tying kit in my vest. I spent hours putting it all together, with a special emphasis on midge materials as well as enough fur and feathers to whip out a half dozen of virtually every conceivable dry pattern nature can throw at me. I have used it once, in 1993.
To know the brain. . . is equivalent to ascertaining the material course of thought and will, to discovering the intimate history of life in its perpetual duel with external forces.