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Wild Side: Caddisflies excite trout, anglers

Elk hair caddisfly, magnified about 20 times. Dan Wilcox photo

Caddisflies are small insects that have fascinating adaptations to life in fresh water. Caddisflies belong to the order Trichoptera, closely related to butterflies and moths in the order Lepidoptera. Many species live in the Kinnickinnic and Rush Rivers, providing food for trout and excitement for trout fishers.

Caddisfly larvae are small worm-like creatures that live on the river bed and have to hang on to avoid being swept downstream. Some are vegetarians, eating algae and decaying plant material. Some species are predators, eating other small macroinvertebrates. Many caddisfly species have larvae that build their own houses by gluing small pieces of pebbles, wood or bark around them to form a tubular case of armor. Trout sometimes eat the whole enchilada, case and all, to get the nutritious caddisfly larvae inside.

Many caddisfly species are filter feeders. The larvae spin small nets like spiders to strain fine particulate organic matter out of the flowing water. Caddisfly larvae have species-specific net designs, adapted to different current velocities and substrate types. Some species inhabit rock surfaces, some use silk to tie to the bottom of larger rocks and others cling to wood.

Caddisfly larvae defend their stream bed territories from others, resulting in fairly evenly-spaced distribution of insects and their nets. They even stridulate, making noise like crickets that may help them defend their territories. One species of caddisfly that lives in rivers in this region digs small gouges on the surface of underwater sticks and logs to provide shelter from the current, thereby creating an interesting pattern on the wood that clearly shows the size of the individual caddisfly larvae territories.

Matching caddisflies and fishing imitations is challenging because trout eat larvae, pupae and adults. After a year or two, caddisfly larvae turn into pupae, leave their cases on the stream bed and rise to the surface buoyed by a bubble of gas. The winged adults emerge quickly from the pupal case at the surface, bounce on the water a few times and fly off to mate. The adults are small, usually less than an inch long with six legs, two long antennae and two pairs of wings folded over their backs like a tent when at rest. Females of some species lay their eggs on the water surface while other species lay their eggs on the river bed and then swim back up to the surface. Caddisflies synchronize their emergences, resulting in clouds of flying insects.

All this reproductive activity during emergencies by the normally reclusive caddisflies drives trout wild. Fishing during a caddis hatch is fun. Trout often smack the pupae at the surface with gusto and leap out of the water to nab flying adults.

My favorite caddisfly imitation is the Elk Hair Caddis, a bushy fly that floats well, imitates an emerging caddis adult and best of all; I can see it easily on the water. I keep a few different colors and sizes in my fly box. The real challenge is tying them onto the leader when the trout are rising all over.

I should be reminded by Isaak Walton's Complete Angler (1654) that fishing is a contemplative recreation. When the caddifles are hatching the trout are rising and I'm excited, struggling trying to tie on a fly, I should just sit down on the bank and contemplate the scene. I should also get some magnifying glasses.

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