It was a late summer evening too many years ago, and I was standing knee deep in the Missouri River, several miles below Holter Dam. It was a windless night by Montana standards, the streamside grasses bending but gently. The sun was setting behind the Rocky Mountain Front, and caddisflies were everywhere. They were far less selective than the trout, crawling all over me. Many left their green egg sacs on my waders, which must have looked like tree stumps to them. The trout were having a feast, slurping caddisflies everywhere I glanced. Fly fishing the caddis hatch at times like this is either fulfilling, i.e. many trout netted, or frustrating. This was my first such “caddis event”, and it proved to be the latter. But like everything in fly fishing, it presented a challenge, and over the years I have continued fishing the caddis hatch, until it has become one of my favorite summer hatches.

It may come as a surprise to some that caddisflies make up a greater portion of a trout’s diet than the more celebrated mayfly. There are over 1,200 known species of caddisflies, and such diverse speciation has allowed them to thrive in all the water types present in North America. In addition, adult caddisflies are available as a food source to trout during more months of the year than mayflies.

In his book, “Caddisflies“, Gary LaFontaine summarizes stomach content studies performed on the Missouri River during the months of May through October. In all but the month of August, caddisflies significantly outnumbered mayflies. In fact, they comprised over one third of all food sources consumed by trout in every month studied. Counting pupae as “surface food”, surface feeding was greater than subsurface feeding in all but the early spring months. Given this information, it’s clear that understanding the life cycle of the caddisfly and how to fish its stages effectively should be a part of every well-prepared fly fisher’s armamentarium.

Caddis Lifecycle

Like mayflies, most caddisflies have a one year lifespan. But that is where the similarities both begin and end. While some species of caddisflies lay their eggs on the water’s surface, many dive to the bottom of the stream, where they lay their eggs directly upon rocks and log structure. The eggs hatch into larvae in a few weeks. Most of the caddis lifecycle is spent as larvae, eating plants and detritus found on the stream bottom. Some species are free-living, spending their time hiding in cracks in the rocks. But most build a case of pebbles and other stream-bottom bits, and attach themselves to rocks and logs. Below is a picture of an overturned rock in the Madison River, covered with such cases. Note that they are all aligned with the current, which helps to carry food to the relatively immobile, cased larvae.

While some of these cased larvae are found in trout stomach samples, they make up only a small portion of their diet. From a fly fisher’s perspective, that is good news. Otherwise, how would we present a fly imitating an immobile food source in a flowing stream?

A few weeks before emergence of the adult form, the cased-larvae seal themselves in their cases. The free-living larvae build a cocoon, much like moths and butterflies.  Over the next several weeks, the larvae transform into pupae. When the transformation is complete, the pupae swim to the surface, split their shell, and emerge as sexually mature adults.

Unlike mayflies, which must float helplessly on the surface to dry their wings before taking flight, caddisflies have hydrophobic wings which remain dry. Thus they skitter about the surface for only a few seconds before taking to the air, offering a difficult target to feeding trout. During a hatch, trout can sometimes be seen to leap completely out of the water in apparent attempts to engulf adult caddisflies.

Once the adult flies have taken flight, they congregate in streamside trees and bushes, where they mate over the next several days. After the eggs have matured, the females return to the stream. There they deposit their eggs, completing their lifecycle.

Fishing the Surface

On most streams, caddisflies hatch throughout the day. Sometimes there is a mid-morning peak which will draw fish to the surface. However, most often  the hatch is too sparse to attract their attention. Nonetheless, a caddisfly pattern can be used as an attractor dry fly. This is especially true on smaller streams, where heavy hatches seldom occur, and trout feed less selectively.

The “real event” occurs in the evening, when dusk arrives and casts shadows across the water’s surface. Although we commonly refer to this as the evening “caddis hatch”, much more is occurring. In addition to a hatch, the egg-laden females leave their streamside bushes, and return to the stream to lay their eggs. Some will be dapping their bodies in the surface and dropping their eggs, while others will be diving to the stream bottom to deposit theirs. Consequently, trout will have a diverse smorgasbord to choose from. There will be egg-laying adults, rising pupae, pupae trapped in the film, crippled or spent adults, and airborne adults skittering across the surface. The fly fisher will of course be faced with the same choices, and must decide which flies and tactics to use.

For the dry fly purist, fly fishing the caddis hatch can be a frustrating experience. Trout will usually seek the most easily taken food sources, which in this instance, are the pupae. However, if one studies the water during this feeding frenzy, an occasional snout will be seen breaking the surface, offering a target for dry fly fishing. But unlike a mayfly hatch, an imitation fly presented “dead-drift” will usually be refused.

Noted author and fly fisherman, Leonard M. Wright Jr., spent a great deal of time trying to solve this dilemma. His studies culminated in his book, “Fishing the Dry Fly as a Living Insect“, published in 1972. After much study, he concluded that the caddisflies emerged upstream.  He tried imitating this by twitching his dry flies in a variety of ways, that is sideways, downstream and upstream. He concluded that only an upstream twitch consistently led to a strike.

With this observation, he developed a presentation that begins by casting across or across & downstream.  The fly is positioned in the trout’s feeding lane. When it has drifted to within several feet of the trout’s lie, a twitch or two is added, while the fly continues its drift to the waiting trout.

He also experimented with different types of flies, and created the fluttering caddis pattern. This pattern is much easier to twitch effectively than a flush-floating fly. I have tried his methods, and they do work. Below is a picture of a fluttering caddis pattern, tied according to his recipe.

Another dry fly tactic is to imitate a trapped or crippled caddis. The X-caddis, developed by Craig Mathews and John Juracek at Blue Ribbon Flies in West Yellowstone, is a very effective pattern for this. It floats flush in the surface film, and is fished dead-drift. Here is a picture of an X-caddis.

Fishing the Film

If one is not irretrievably committed to dry-fly fishing, try fishing the film with pupae imitations. It is the most effective means to fish the evening caddis hatch. The early English fly fishermen, circa 1450, were probably doing exactly that with their winged, wet flies, which closely resemble an emerging pupa, as seen below.

More recently, a variety of flies have been designed to imitate this stage. The most well known of these may be Gary LaFontaine’s “emergent sparkle pupa”. I am not a particularly gifted fly tier, and so I keep it more simple. When fishing the film, I use a wingless, traditional wet fly, tied 6-8″ off the bend of a fluttering caddis pattern. I cast this combination slightly across stream. At the end of the drift, I swing it below me, and twitch the flies time or two. If nothing happens, I bring the wet fly to the surface, like an emerging pupa. Strikes may occur anywhere along the drift, but they most frequently occur when raising the wet fly to the surface.

Fishing the Subsurface

If fishing the film isn’t working well, or the fish are on the small side, I change tactics, and fish subsurface. Using a sinking tip line, I attach two wet flies, tied with different colors. I prefer tying them with a bead thorax, as shown below.

With this set-up, I cast across-stream, and throw upstream mends as needed to allow the flies to sink in the water column. I then follow the drift downstream with the rod tip, keeping a tight connection. I stop the drift several times, bringing the flies to the surface, simulating emerging pupae. If I don’t get a strike, I simply lower my rod and allow the drift to continue another 5-6′ before stopping it again. This is a particularly effective tactic  early in the hatch, and attracts larger fish. Trophy trout are usually hesitant to come up to the surface, even during the evening hatch.

Fly fishing the caddis hatch offers many opportunities, and as seen, can be fished in a variety of ways. I would suggest that you try them all, and see which you prefer to use. But as always, be flexible- one tactic doesn’t work all the time.

Written by Al Simpson, November 2015.                                               Edited November, 2016.