Fishing the Iris Caddis

Many of you have emailed me asking about how and why we fish that magical summer evening pattern, the Iris Caddis.   

Late May through September is the  time of year when the Spotted Caddis (Hydropsyche sp.) becomes an essential trout food, most particularly in the two month period from late June through Early August. Here in North America, they are very abundant and they are present in just about every river where trout are found. And most importantly, trout love these little buggers. The past few weeks my most productive surface fly by far has been an emerger imitation - the Iris Caddis. The adult natural has a tan/grey body and wings that are ginger mottled with darker, so we tie them with a tan body with a grey tone.  They are typically a size #14-18; I mostly fish a size #14 on a standard shank length dry fly hook.

Understanding the behavior of this particular aquatic insect is essential to being successful when they are actively hatching. You don't need to be an entomologist or know any fancy language either, just some basic identifying information, and you are good to go.

How many times have you been on the river in the evening and witnessed trout aggressively rising yet there are no insects on the water surface? And yet at the same time, you see caddis fluttering about 6-10 inches above the water in clusters? These two questions are the answer to what you should fish - a caddis emerger. More specifically, a tan Iris Caddis dead-drifted right in the surface film - see prior post on tying the Iris Caddis. 

So what is happening? The caddis pupae swim up from the river bottom and while suspended in the meniscus preparing to hatch, they drift with the current and work to free themselves of their pupal shuck. Once they have separated their new skin from the old, they literally pop out into the air without spending even a nanosecond on the surface as an adult. That is why you only see the adults in the air, and that is why the emerger works so well - the pupa are very vulnerable while preparing to hatch, and the trout know it. The trout feed aggressively because they know they have only seconds once the pupae get to the surface before their meal becomes airborne.

Often, the following morning, the adults will return to lay their eggs in the softer water and eddies along fast runs and flowing pools.  An adult caddis pattern or spent caddis pattern will take the fish rising to them.

And finally, I do know a few anglers that fish this pattern subsurface as a nymph or wet fly, and do quite well.  One of these anglers, with whom I reluctantly fish with,  likes to remind me of this fact ad nauseam. : ) 

Sharpen your hooks.