Caddis - Trichoptera
Only a handful of caddis species are free living, the rest construct some sort of housing to carry around as protection from predators. All manner of available materials can be used to construct these houses from tiny pebbles glued together with silken threads to bits and pieces of chewed up woody debris. Each species having its own preference.
I have performed thousands of gastric lavage samples on fish throughout the western united states, and have observed on most occasions, some indication that fish routinely ingest cased caddis. On rivers that have large concentrations of caddis such as the Brachycentrus species, the cased caddis can be a beneficial opportunistic meal providing sustenance when other hatches are sparse.
Debris shelter builders are frequently preyed upon because the larva move around along the stones more freely than many of the stone shelter builders as they feed. The shelter building caddis belong to the shredders and scrapers functional feeding group, they are a lot like the cows and sheep of the aquatic insect world both in grazing habits and forming large herds. Shelter building caddis tend to hatch in vast quantities in shorter durations but the cased larva are available for a large portion of the year.
Free Living Caddis
Caddis larva are broken down into three distinct groups, the free living, net spinning and case/shelter building groups. Each of these groups have distinct behavioral characteristics important for the angler and fly tyer to understand. Free living caddis are predatory in nature, do not build shelters but rather, crawl freely about the rocks in search of other macro invertebrates in which to feed upon. Net building caddis spin funnel shaped webs and feed on detritus filtered from the current captured in the nets that they construct. Shelter building caddis build protective shelters that they carry around with them as the crawl amongst the cobble feeding on the bio-film that grows on the rocks.
It is interesting to note that free living caddis larva species emerge in small numbers throughout the season and are always available as opportunistic prey items throughout the day and long into the evening. Emergence activity of the free living groups will typically be in small but predictable numbers all season long. This makes them a top choice for the angler to imitate when no specific hatch activity can be observed. I generally prefer to start my angling day with a heavy Czech or two nymph probing shallow to medium depth riffles — up to three feet — hoping to take advantage of opportunistic feeding activity and switch to a caddis emerger pattern when I actually detect emergence activity.
My favorite color combination of Czech nymph. One of that I frequently run out of in my fly box as I am always giving them away.
I originally devised this color combination to cover the yellow/green stones of summer. I use this fly when the Yellow Sallies are hatching. Even when the Sallies are not hatching, this color attracts a lot of attention.
New inventory being tied soon.
Another Czech nymph that I adapted to match the size shape and color of the Hydropsyche caddis that I have been sampling around the west. I find plenty of these in spring gastric samples to indicate that this is nymph of significant importance. My angling logs agree.
Riffle Drifter Perdigones
Optimized to fish shallow riffles, where free living caddis live, the Riffle Drifter series offers an ideal pattern for the fast pace of euro-nymphing choppy riffles such as on Montana’s Madison or Oregon’s Deschutes Rivers. A great Rocky Mountain freestone pattern.
Caddis Pupa - Emergers
Of all the members of the EPT group, caddis are the only family to undergo a complete life cycle: larva, pupa, and adult. The pupal form is the transitional stage between either a sheltered dwelling or free-living caddis larva and the winged adult. Free-living caddis larva only build protective shelters of debris or stones that they seal themselves inside during pupation. Caddis pupa are only available at the time of emergence and in most cases, emerging pupa is the most vulnerable stage in the insects life cycle that is available to trout.
It has been debated over the decades the theory that caddis inflates their exoskeletons with a gas bubble to emerge to the surface. While I have not seen this phenomenon in person, I have seen tiny flashes of light near the surface of the water like that of the paparazzi shooting a movie star walking the red carpet. I have surmised that I was witnessing the glints of light as caddis emerge encased in this so-called gas bubble. Because of this phenomenon, I fish with caddis emerger patterns that imitate this gas bubble to some degree at or very near the surface instead of presented deeply. When fishing deeper in the water column, I use much less flashy, more opaque caddis pupa imitations because they have not begun to exhibit this gas bubble yet.
I have observed several caddis species whose exoskeleton would exfoliate in the process of emergence. The chitin of the pupa would be somewhat transparent allowing the more colorful adults’ abdomen to show through. Patterns such as my CW Softie imitate this occurrence. Either way, I strive for a bright yet transparent effect when designing caddis pupa nymphs.