Caddisflies live under water as worm like larvae. They take one of two forms. Many are cased, carrying around homes of sand and pebbles, sticks and stones. These generally live in the slower water of runs, flats, and pools. Others are free-living, without cases. Some free-living larvae construct crude shelters into which they can retreat; others roam freely without any shelter at all. Free-living caddis larvae are most abundant in the fast water of riffles and brisk runs. We have divided the Trichoptera order into five distinct groups: Free living caddis, saddle case caddis, micro caddis, tube case caddis, and net spinning caddis. Each group will be explained by pointing out the major differences bewteen them.
Intro:
Caddis pass through a transitional pupal stage before becoming adults. When ready to pupate, a caddis larva either seals its existing case to bottom stones or constructs a case if it doesn't own one. The larval cycle lasts most of the year; the pupal stage lasts a few weeks. When the transformation is complete the adult caddis is wrapped lightly inside the pupal skin, which traps tiny bubbles of gas. It cuts out of the case and is buoyed to the surface by the trapped gases. In some species this float to the top is aided by a strong swimming motion. Other species merely rise at the whim of the water. In either case they are very vulnerable to feeding trout.
Caddis break through the surface quickly, cast the nymphal skin, and fly off toward streamside vegetation in a hurry. They leave a lot of splashy rises in their wakes.
The moment of most vulnerability for an emerging caddis is the pupal ascent to the top, especially in the instant before it reaches the surface to break through. When a caddis hatch is on, trout often leave their stations and hang suspended a foot or two beneath the surface, waiting to intercept helpless pupae.
Caddis adults have tent like wings pitched over fat bulbous bodies. They mate in the leaves and grasses alongside the stream. Many species return to the water to lay their eggs by dancing and tapping their abdomens on the waters surface to wash off the egg clusters. But others actually dive down under the water, swim to the bottom, and deposit their eggs on bottom stones. The first group causes excellent dry fly fishing; the second group, once it is understood, can give you excellent wet fly fishing.