Caddis are abundant in most of the trout waters in the Northwest.  In rivers like the Deschutes, caddis larva and pupa can number in the thousands per square yard of river bed.  In many rivers they are the most consumed food item during the mid-summer months. Caddis flies are of the insect order Trichoptera, which means hair wing. All caddis have fuzzy wings. Like butterflies and moths; caddis go through a true metamorphosis.  They have a larval, pupa and adult stage.  All stages are vulnerable and are eaten by trout.  Essentially a caddis larva fills the role of a caterpillar.  It is this juvenile stage which does the feeding and growing.  In many ways caddis larvae do resemble caterpillars.  They have large heads with well developed mandibles, cylindrical bodies and short powerful legs.  However unlike caterpillars, many caddis species build houses from  gravel or vegetable matter.  Some of these houses are stationary, many are mobile.  Most species of caddis larvae that build houses are grazers that scrape algae from the rocks for food. Some species of predacious caddis larvae roam unencumbered in the substrate.  They eat other smaller smaller aquatic insect juveniles. Some species build funnel shaped webs that are strung between the rocks on the river bed.  The widest part of the funnel faces upstream with the larva living in the down-stream neck of the funnel.  Its head is always pointed upstream into the current.  Food items get caught in the bell of the funnel and the larva can feed at leisure.   By utilizing this web strategy, they are very much like spiders. Some of these net spinning species are herbivorous others are predacious.  

  Caddis larva come in a wide range of sizes and colors. The ones that build housed from solid matter such as stones or woody debris are often brightly colored.  They may even be shades of bright yellow or pink.  Many species of larvae are green.  Some are nearly fluorescent green.  Others are olive tones.  Green tones are prevalent both in species that do and those that don't build houses.  Most species that do not build armored houses are camouflaged with earth tones.  Most of these larvae are olive or brown to tan tones.

  Laval populations of many species go through predictable “behavioral drift” cycles where they are consumed by trout and white fish in great numbers.  Several times while growing up, each house building larva will outgrow it's house, discard it and drift free while searching for a site and materials to build a new larger one.  While in the house hunting/building mode, they are exposed to the elements.  Numerous larvae might outgrow their houses at nearly the same time and be drifting down along the river bed enmass.  You can imagine that a hail of brightly colored juicy caddis larvae might have a similar effect on a population of trout as throwing a hand full of popcorn to a flock of pigeons.  Species that build webs usually use a slightly different strategy for finding new homes.  Since the are able to build a strand of silk, they often rappel themselves down stream like climbers coming down a cliff face or a spider dropping from the ceiling.  In fast currents they can become like kites on the end of a string.  During these migrations many are exposed to feeding fish.

  When each larva has reached maximum maturity it crawls into a protected niche and constructs a cocoon.  Metamorphosis starts to change the larva into an adult insect.  It develops wings, feelers, long legs and sex organs.  This complicated transformation can take weeks.   During this period the insect is unavailable as trout food except during catastrophic drifts caused by floods, wading anglers, etc.

   When the metamorphosis is complete, the newly formed adult insect chews an exit hole in one end of the cocoon and crawls out.  It is now an air breathing organism surrounded by water.  To protect it, the insect is partially covered by a membrane which contains air.  Like most terrestrial insects, caddis breath through tiny holes in the sides of their abdomens.  The air retaining membrane covers the whole body, but is most prominent in the anterior region.  This  air bubble is highly visible to predator fish.  It is often the most distinguishing feature which fish key on.

  Since air is a gas, it may be compressed or expanded.  In deeper flows the pupal membrane is compressed close to the body by water pressure.  As the insect nears the surface, this membrane will expand with the decreasing water pressure. 

  Some species of caddis drift for long distances within inches of the bottom until they achieve the strength and buoyancy to rise to the surface.  During the early stages of the hatch, patterns like the Nori Caddis Pupa or Bead Head Caddis Pupa are most effective when fished close to the bottom. As the hatch progresses and more insects are rising to the surface a LaFontaine Sparkle Pupa can become more effective.

   Most caddis hatch by fighting their way through the surface film.  The pupal shuck bursts as it comes in contact with the decreased pressure of air above the surface of the water.  A hole opens in the top of the pupal shuck and the adult insect crawls onto the surface of the water.  At this point some species ride the surface of the water for a short time and then fly off.  However, according to my observations most small caddis species which hatch from the Deschutes don’t fly, they walk across the surface of the water to the bank.  While traveling to the beach they are vulnerable to the trout which often rise and take these insects very quietly.  Fishing a LaFontaine Emergent Sparkle Pupa dead drift, in the surface film with only the wing greased can be very effective.  Also an Elk Hair Caddis can bring strikes.

   Some caddis don’t hatch from the water but prefer to swim to the shore to hatch.  They crawl out of the water with their pupal shuck intact.  A prime example of this activity is the large October Caddis Dicosmoecus.  With this type of hatch dry adult patterns or only useful when the females return to the water to lay eggs.

   Egg laying flights can result in some great trout feeding activity.  There are three major styles of caddis egg laying; dipping, broadcasting and diving.     Dipping caddis fly an erratic path over the water and dip the tip of their abdomens to the surface and deposit one or several eggs at a time.  This flight is unpredictable and hard for trout to time.  Although this type of egg laying activity is easy for the angler to see it usually draws little attention from the trout.