Fly Fishing With Rock Worms

There is no doubt that trout eat caddisflies in their larval and pupal forms. It is interesting to note that they also eat caddisflies of the cased variety when available.


As a youngster, I was often given the chore of cleaning the day's catch and preparing them for the table. During the cleaning process my dad would tell me to cut open some of the stomachs to see what the fish had been eating. "There are rocks inside them," I would say. "They've been eating rockrollers," was dad's reply. Being ignorant of entomology at that age, I was left to assume, as I did for several years, that trout were like birds and needed to eat rocks and pebbles to help grind and digest their food. Over the years I have learned that these rocks were the remains of cased caddisfly larvae, and trout eat them case and all.


Let's take a look at some of the patterns that have been developed over the years to imitate cased and non-cased caddisfly larvae and pupae. In 1925 Franz Pott of Missoula, Montana, was issued a patent for an artificial fly called the Rock Worm. It was made as a definite attempt to imitate the larva of a caddisfly. The weaving process was tedious and the pattern only enjoyed a short life. This is interesting to note because it shows that fly fishers in the 1920's were aware of cassisflies and knew them by the common name rock worm. Pott went on to create his "mite" style of hair hackled flies, which gained a strong following in the Rocky Mountain region.


The mite style gets its name from the hellgrammite, which is what early fly-fishers in the West called the stonefly nymphs they were finding in many of the river systems. The stonefly nymphs were similar to the dobsonfly nymph (hellgrammite) that they were familiar with from the East.


Many of Pott's mite flies resemble caddisfly larvae more--in color, size and silhouette--than they do the stoneflies. Trout probably take them for caddisfly larvae and emerging pupae. The reasoning behind this assumption was brought out by George Grant. Grant lived through this period of fly-fishing history and was very familiar with the Pott patterns and their history. Grant suggests that, "Almost all Montana anglers were wet-fly men before 1950." The techniques employed by wet-fly fishers include the up-and-across dead drift method, the down-and-across swing method, and the hand-twist-retrieve method. These techniques imitate the behavioral drift and emergence of some species of caddisflies.


In Fly Fishing the Rockies by William C. Black (Pruett Publishing, 1931): a paragraph compares the Pott flies to caddis: "...Caddisflies were always plentiful on the South Fork....free swimming caddis pupa, the immature form between the larva and the adult fly, has long trailing legs and antennae, very much like the stiff, bristly conformation of the Pott's flies. The color and size match happened to be quite close too, and further, the trout sometimes hit an actively manipulated nymph with great eagerness, as if it were a swimming pupa."


Another reference to the Pott's flies as a representation of caddisflies can be found in Fishing the West, Macmillan Company, 1950, by Arthur H. Carhart. Carhart writes that Pott began tying his own flies because the ones he bought were not durable enough. "This led to his tying his own flies, and one of the natural foods he tried to simulate was an insect locally called the rock worm. The color varied, in different locations, from a sandy color to almost black. Instead of the soft feather hackles which lie against the body of the fly when wet, Pott tied in a stiffer hair which would give the lure some motion and would stand out so the hook point wouldn't get caught so readily in rocks and other underwater obstructions."


There have also been attempts to imitate cased caddisflies. Paul Young began tying a pattern called the Strawman. The original Strawman was tied with loosely spun deer hair along the shank. This was clipped to shape, and a yellow floss rib was wound through the hair and tied off behind the hook eye. This pattern is tied to imitate caddisfly larvae that use small pieces of bark and sticks to make their cases.


Charles Brooks tied a fly he called the Skunk Hair Caddis. It was tied to imitate caddis larvae thet build their cases out of small stones and grains of sand. The fly is tied on a 2X long hook shank in size 6 through 10. The secret to tying the fly is to find a skunk tail that has hair fibers at least 4 inches long. The fly has a copper rib that helps hold the hair together after repeated chewing by trout. The rib is tied in at the front and wound toward the rear of the fly and then back toward the front again. The skunk hair is twisted and then wrapped forward forming a segmented body. The fly is finished off with one wrap of a soft, black hackle. Charles claimed, "It is the best cased caddis imitation I know of, and has taken many fish for me over twenty some years."


In more recent years, fly tiers have used peacock herl, clipped hackles, twisted yarns, pheasant tail fibers, turkey biots and a combination of these materials to form cased caddis imitations. An interesting example of a cased caddis imitation, called the Garbage Can Caddis, utilizes all the waste materials from a tying session of different patterns. I first saw this tied by Jack Dennis. Jack took a pile of "garbage" out of his tying trash bin and spun it into a small rope between a loop of tying thread. After this was twisted tight, he wound it on his hook shank, tied it off, and then trimmed the material to shape. With the combination of deer hair, elk hair, moose hair, feathers, scraps of yarn, tinsel and dubbing, the finished fly makes an attractive artificial cased caddis.


There are species of free-living caddisflies available to trout predation also. These caddis have been imitated with twisted yarn bodies such as the Serendipity, or with more complex woven bodies, such as those tied and fished by the Polish International Fly Fishing Teams.


Fly tiers can make an effective cased caddis pattern by using a chain-stitching technique.


The Chain-stitched Rock Worm is a pattern that imitates a caddisfly in a sand and small stone case. By varying the colors of flat waxed nylon thread, a tier can duplicate the color of cases found in any stream. The size of the case can be controlled by adding or deleting strands of waxed nylon thread as needed.


A collar of color should be added to the pattern just in front of the case. It can be a small pinch of dubbing or a few wraps of floss. This is an important feature. In his book Caddisflies, Gary LaFontaine explains: "The study of the actual caddisfly larvae drifting with the current revealed a number of previously unknown characteristics. The main trait betraying the insect as a live food was the movement of the larva in and out of the case. The wriggling motion exposed a contrasting band of body color between the head and case." The band of color most commonly used is bright green, yellow or tan. Try to match the color to the caddisfly you are trying to imitate. A soft hackle should be added to the pattern just in front of the colored collar. This will simulate legs and help create lifelike movements.




This article first appeared in Fly Fishing & Tying Journal, Summer issue 1999 by Robert Williamson