Waterboatmen and Backswimmer Pattern

I have had a few e-mails this past week asking me about my favorite patterns for Backswimmers and Waterboatmen. So here is my take on these two groups:

Backswimmers are in the family Notonectidae and Waterboatmen are in the family Corixidae. Both of these families are in the same insect order (Hemiptera = True Bugs) and can generally be imitated with different sizes of the same pattern. There are many other families in the True Bugs group but most are terrestrial, and the few that are semi-aquatic are seldom important to fish. Backswimmers and Waterboatmen however are in a class all of their own; and form a large part of a trout’s diet in the spring and fall when the adults are most active and most abundant.

Backswimmers and Waterboatmen have a one year life cycle and go through incomplete metamorphosis. Overwintering adults lay eggs in the spring and die shortly afterwards. The eggs hatch and juveniles that look like miniature versions of the adults, but without wings, spend the summer feeding and growing through five instars. The fifth and final moult produces a fully winged adult that for the most part continues its underwater existence. The forewings are generally dark and leathery and lay overtop of the flight wings which are thin and transparent. Large oar-like hind legs allow them to swim effectively under water.

The ability to fly allows the adults to move from one water body to another. This allows the adults to move to other locations should their wetland dry up, or to simply look for other water bodies to colonize. On warmer, calm days in the spring and fall you will often see the adults dropping onto the surface where it may take them a second or two to penetrate the surface film and dive to cover. This is when they are at their most vulnerable. They are also vulnerable when they dash to the surface to replenish their air bubble that allows them to breathe under water.

As to fly patterns there is really no need to get overly complicated; the basic parameters of size, shape, and color are really all you need.

Many patterns call for a 1XL hook, but I prefer a wider gap in relation to the hook size so I usually fish a standard wet fly hook in size 14 or 16. Backswimmers tend to be bigger than Waterboatmen so if you specifically want to imitate them you could go to a size 10 or 12. But Waterboatmen generally outnumber Backswimmers 50:1 – which is why I usually fish the smaller sizes.

Stout bodies of chenille or dubbing with a darker over wing of turkey quill, and some rubber hackle legs are standard and will give you the silhouette you need. A small bit of silver tinsel is often tied in near the rear end to simulate the air bubble that they use as an underwater lung. If you want your pattern to stay in the surface film, an over wing of black foam is the way to go.

The theory behind color is that you want to match the color of the surrounding habitat. And it is a sound theory – but rather than waste time tying various colors to suite different condition I tie all of mine with silver Mylar tinsel chenille which tends to reflect the color of the surroundings. It also ads a little sparkle to simulate the air bubble that they typically carry. Quick and easy to tie – and they catch fish.

Waterboatman pattern - this one is tied with the foam back

                    Hook: standard wet fly, #14 or 16

                    Thread: 6/0 black or brown

                    Body: silver Mylar tinsel chenille, medium (2 wraps only)

                    Wings: mottled brown turkey quill, or black foam

                    Legs: rubber hackle, brown or black

For a few tips on how to fish it, see my earlier post: Top Pick for Fall Trout.