The Sowbug (Cressbug, Isopod)

The Sowbug is a widely distributed crustacean from the suborder Isopoda. Found in most lakes, ponds and slow moving bodies of water they are also prevalent in many tailwaters as well. Where they are present they often form a substantial portion of the trout's diet. Characterized by a flat profile, a hard back, legs sticking out the sides of the body and two (or more) prominent antennae they are not a difficult food form to imitate. The pattern given here was developed from a pattern brought back from the White River in Arkansas by Phil Brandt.


Hook: Mustad 3906 #16 or equivalent
Thread: Black
Antennae: 2 Natural Goose Biots
Ribbing: 5X Tippet
Back: 1/8" wide strip of scud back or clear irredescent plastic
Weight: .015 dia. heavy soft wire (lead substitute)
Dubbing: Gray Hareline Dubbing or Gray-Olive Nymph Dubbing


1. Start the thread at the front of hook and wind to the bend. Attach two goose biots approx. hook gap in length forming the antennae or what looks like a split tail.
2. Wind the thread to the front of the hook lashing one end of 3" of 5X tippet material to the side of the hook. The other end should stick out the back of the hook.
3. Wind the thread to the bend of the hook attaching one end of the 1/8" wide plastic or scud back to the top of the hook with enough sticking out the back of the hook to later be pulled forward to form the top shell of the sowbug. At this point you have the two biots, the ribbing and the shell material all sticking out the back of the hook with the thread at the bend.
4. Take about 2" of the wire and wrap it tightly around the center section of the hook forming a tight spiral from approx. 1/16" forward of the bend to 1/16" back of the eye. This usually takes about 8 wraps of wire.
5. Wrap the wire with thread in a criss-cross fashion. When finished the wire should be almost completely encased in the thread. Complete the wrapping process with the thread at the bend of the hook. Apply head cement to the thread encased wire and let it dry.
6. Using a non-serrated pliers or hemostat flatten the wire to form the thin profile and wide back of the sowbug.
7. Apply the dubbing to the thread and wrap it around the flattened wire dubbing forward to just behind the eye of the hook.
8. Grasp the 1/8" plastic and pull it forward over the top of the dubbing. Secure it in place just behind the eye of the hook with a couple of turns of thread. Trim off the excess sticking out over the eye of the hook.
9. Spiral the tippet ribbing forward in an open spiral over the top of the dubbing and plastic to just behind the eye of the hook. Secure it in place with a couple of turns of thread and trim off the excess.
10. Whip finish just behind the eye of the hook and cut the thread.
11. Pick out the dubbing just a little only on the sides of the body. Trim any excess dubbing sticking out on the top or the bottom of the fly. This forms the characteristic legs sticking out the side of the body and also helps accentuate the thin profile and wide back and bottom.


This is a slow water fly fished on a dead drift as close to the bottom as possible. It is usually fished with a strike indicator so that it drifts just above the bottom of a tailwater. When fished in a pond or lake it is often fished with a sinking line and then moved along slowly just above the bottom. It can also be fished in a pond or lake by allowing it the sink to the bottom and then using a series of slow short retrieves allowing it to again sink between each retrieve.