Welcome to Not Quite Entomology

Welcome to Not Quite Entomology! This is a different approach to matching the hatch, or learning which insect the fish are really eating. The flies and methods to make it all work will be here as well. We hope this series will inspire you to go out, look on top of and under rocks, check the stream-side vegetation, really investigate your favorite water and learn which are your local trout's favorite foods!


By LadyFisher

Our insect this time is one of the common freshwater crustaceans. There are over 1,100 known species in just North America! They live in all kinds of freshwater places, usually for our purposes though, in tailwaters and spring creeks.

These crustaceans are very important food sources for fish. The two larger forms are the Aquatic Sowbugs Ispoda and the Scuds Amphipoda. Since both are about the same size, 5 to 20 mm, we are lumping the two together here.

<i><b>Asellus</i></b> adult The Asellus shown left is the most important of the sowbugs, with about 100 species. They live in a variety of shallow freshwater environments, among rocks and decaying leaves. The common name for sowbugs, (and sometimes the scuds too) is cress bug since they are found in spring creeks and other clean, clear water which grows watercress. The fly which imitates the sowbug in slow-flowing water with considerable plant growth is the American Sowbug.

There are several important species of scuds. The group totals about 90 in North America. Most are found in the same places as the sowbug, with one important exception. The family Haustoriidea has only one species in North America, and it is important because it is found in an entirely different environment! The Pontoporeia hoyi lives on the bottom and open waters of deep, cold lakes.

Gannarys adult

The most important specie to fly fishers is the Gammarus. This one also lives primarily in shallow waters of all kinds. They have a strange habit, as they swim they move to the side, and are called 'side swimmers.' These are not shrimp, although in Canada, scuds, sowbugs and shrimp are all called freshwater shrimp. Colors are varied, from grays, browns and cream to the most common olive and greens.

Scuds are interesting in the fact when they are disturbed or under attack, they roll up, like an armadillo. That may be why the so-called scud hook was invented. In reality, the scud when swimming, swims straightened out. The body at rest or swimming is not curved. Tie your imitations on a stright-shank hook.

There are many specific fly patterns for nymph fishing based on scuds. These include the Yellow Freshwater Scud which imitates the Gammarus minus, Olive Freshwater Scud Gammarus fascaitus, Tan Freshwater Scud Crangonyx gracilus , and Tiny Olive Scud Hyalella azteca. Others include Werner's Shrimp, Otter Shrimp, Nyerges Nymph, Henry's Lake Nymph, Big Horn Shrimp, Yellowstone Scud, Fred Arbona's Scud, and the Troth Scud.

Scuds do not hatch. They don't crawl out of the water like the large stoneflies and become wonderful winged creatures. The adult forms shown here are all there is.

Your best bet to catch fish on scuds in lakes is to get your fly down to near the bottom. A weighted fly is the answer in deeper water. Retrieve very slowly. Folks have called scud fishing the most boring of all, since the retrieve should be about as slow as you can stand it. In water deeper than five feet, a sinking line is recommended.

For spring creeks and tailwaters, a floating line with a strike indicator is the way to go. Use a normal nymphing technique, but with again a very slow retrieve. Your fly needs to be on the bottom of the stream bed.

For more on scuds and the flies, read Tailwater and Spring Creek Favorites, Al's C-B Scud, and Sowbug. ~ LadyFisher

Credits: Information and drawings from Aquatic Entomology by W. Patrick McCafferty, published by Jones and Bartlett.

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