So, you want to learn bugs? A good place to start is at the beginning. Lets start at a place in time before there were fish, much less fishermen. In this time there weren’t even dinosaurs. It was the Age of Insects.
In this age, hawk-sized dragonflies chased mayflies sporting wings taller than puppies. Cave children cowered in their shadows. This was a long time ago. . .two to three hundred million years ago to be exact.
The life process for these bugs was simple. They ate, mated, and laid eggs. The eggs hatched into nymphs that, if you squinted your eyes real hard, looked pretty similar to the adults. These nymphs had six legs, three body parts (head, thorax and abdomen) and buds on their backs containing nascent wings. They didn’t have an internal skeleton, but their chitonous skin gave them structural integrity and prevented their guts from spilling out all over the place. They called this skin an exoskeleton.
The exoskeleton was good, but it had a major fault; it didn’t grow. As the insect grew, the exoskeleton would stretch and distort and finally split open between the shoulders, allowing the bug within to crawl out. This process called molt or ecdysis would prove to be of extreme importance to flyfishers.
The freshly emerged bug would be contained within a new exoskeleton that was slightly larger than the old. With each ecdysis the newly emerged bug would have larger and darker wing pads. After a dozen or so such molts, the adult, sexually mature version of the nymph would emerge wearing a set of wings in place of the wing pads. This evolution from egg to nymph to adult was called simple or incomplete metamorphosis.
Millions of insect species roamed the countryside and they competed vigorously among themselves for food, real estate, and luscious mates. Choice niches were occupied by those insects best adapted to that niche. Ripe fruits high in a tree were garnered by those bugs adapted to flying high. Nutritious algae beds in fast turbulent waters were harvested by those insects with strong clingy legs and low, sleek profiles. Insects specializing in chasing down and devouring other bugs became strong of jaw and fast of wing. Over the eons a wonderful order evolved.
Somewhere in the scheme of things a group of insects radically changed their means of development. Instead of evolving from egg to nymph and then on into the adult forms, their eggs hatched into soft bodied, worm-like creatures. Freed from their life long nymphal templates, these larvae, as they were called, could utilize previously bypassed niches.
The larvae exploited every conceivable space. They roamed the crystalline brooks, springs, and tarns of the world’s tallest mountains. They burrowed into muck, feces, and putrefied flesh. They basked in sulfurous hot springs and bathed under arctic snowfields.
Regardless which habitat the larvae chose to occupy, all would enter a period of pupation from which would evolve the adult form. Some pupae such as the cocoons of moths would remain tightly fixed to a single location while others, like the caddisfly pupae, could move about quickly and efficiently.
Unlike the adults of incomplete metamorphosis which looked closely akin to their nymphal selves, the adults of complete metamorphosis were limited only by the whim of evolution. Creatures as diverse as swallowtail butterflies and carrion beetles shared the common bond of complete metamorphosis.
All of today’s insects undergo either complete or incomplete metamorphosis. During a hatch, the differences between the two in both appearance and behavior is profound. Many anglers carry a bizzare array of nymph, larvae and pupal patterns. The fly shops have taught us well because they have a vested interest in filling our boxes with a complete assortment of these flies.
How many anglers actually understand the vagaries of fishing these patterns? Why do we insist on calling it "nymphing" when we fish with a larva or pupal imitation? In other articles we will explore these differences and learn exactly which flies presented in exactly which manner will best exploit these differences. In short, you will become a better angler.