This month's "Fly of the Month" patterns focus on three classics that imitate the net spinning caddis in its larval, pupal and adult stages. All of these patterns are proven fish catchers. No western trout fly fisher should be caught short without them in his or her fly box.
by Jerry Neuburger
A net spinning caddis
The green caddis rock worm
The club's next scheduled outing after the February 11th striper clinic is a March 31st outing on the U.C. Davis property on the Yuba River between Marysville and Grass Valley. The property is known for its feisty rainbows and, in the late fall and early spring, migrating steelhead. Any club member planning to join the club outing to this special water should have a good selection of trout flies in their box and part of that selection should be three of the four stages in the life of the net spinning caddis.
This aquatic insect is one of the most common in western streams as well as those of the Rocky Mountains. Valley varieties of this insect begin their peak periods of emergence in late March through June, sometimes in hatches so thick you have to breath through your teeth when on the stream. They, unlike the delicate mayfly, can live in slightly warmer and more polluted water, making them a "go to" pattern when first approaching a new stream or river.
Caddis flies, unlike mayflies, go through a complete four stage metamorphous, egg, larva, pupa and adult. The net spinning caddis starts its life as an egg, oviposited below the surface film of the water by a female adult. Once at the bottom of the stream, the egg hatches and a caddis larva emerges. The larva builds a net house out of a silk similar to that spun by silk worms. The net, built on the under surface of rocks in the stream collects various bits of debris, some of it edible that the larva lives on and grows. If you're wading, pick up some of the rocks in the moderate flow areas of the stream and you'll see a mushy appearing bunch of algae. Pull the "nest" apart and you'll discover the caddis larva that was the builder.
Caddis pupa
La Fontaine Sparkling Caddis Pupa
After a number of months, the larva grows to the point where it is ready to enter into the next life stage, the pupa. The larva seals itself in its nest and matures into a pupa, the process taking as much as a month. When complete, the pupa swims to the surface, the outer casing splits and the adult emerges. The entire process from egg to adult can take as much as a year while some species reproduce twice in a year.
These caddis are vulnerable to predation by fish at all three stages, larva, pupa and adult. The first of these periods is when the larva engage in what scientists call behavioral drift, a form of migration. The larva crawls from its nest and drifts downstream for a distance before grabbing on again and spinning a fresh net. This drift occurs throughout the day but has high points in the early morning and early evening.
The second period where the caddis is vulnerable is when the pupa emerges and swims to the surface. As part of its emergence, a gas bubble builds inside the pupa, allowing it to rise. This bubble is a shiny target for a hungry trout. Once the pupa reaches the surface, it floats along for a very short period as the adult emerges from the casing. Emergence usually starts in mid afternoon and builds in volume to just before sunset.
An adult caddis
Elk Hair Caddis
The last period of vulnerability is when the caddis reaches the adult stage. As it emerges from the pupal case, the insect needs a few seconds to inflate its wings, giving it the ability to fly. The adult floats on the surface of the stream, a large target. The adult female is also vulnerable during the stage where she is ovipositing eggs since she dives into the stream, swims to the bottom and deposits a string of eggs before swimming back to the surface. The "magic hour" experienced by many western anglers is frequently a product of the evening caddis hatch and the ovipositing of eggs by females.
While trout taking mayflies usually "slurp" down the insects with a gentle rise, the rise to a caddis, ready to leave the stream surface within a second or so of hatching, can be quite spectacular, with the trout, especially younger fish, fully clearing the water. If you're seeing very splashy rises, it's a good chance that the fish are feeding on adult caddis.
These flies are normally tied on #12 to #16 hooks with bodies of green, tan and yellow.
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