This is one of my favorite surface terrestrials, as sure a floater as a popping bug, but with much more finesse. The work here is shaping the balsa and attaching it to a short piece of mono filament. But let me assure, it is time well spent, for it is a very efficient fly.
Hook: Mustad 94840, 10-16 (standard dry fly hook)
Body: Balsa wood, colored and sealed with tying cement (or 5 minute epoxy), connected by a short piece of mono filament
Legs: Dry fly hackle
Pretty simple from appearances, but it's not a labor free fly by any means. Shaping tiny pieces of balsa is anything but easy, but a fine emory paper usually does well with a little patience and care not to remove your fingertips in the process. Football shape is preferable, but squared off at the corners will also work on less particular species of fish. Make as many as possible at once. Once they are shaped, a small hole is placed in one end of each piece with a blunt shaped needle. Cut very short pieces of monofilament, dip the end in a small dab 5 minute epoxy (several batches will probably be needed, so don't make too much and waste it. A small dab each time will suffice. Placing the monofilament in a pair of forceps works well to insure the proper gap and keeps the epoxy off of your fingers when the end of the monofilament is dipped. Press the balsa onto the ends (to the forceps), one piece slightly larger than the other. Set aside and allow to set fully.
There are various colors of large species of ants, black: a carpenter ant, red: a red ant, reddish brown: various leaf cutters and others.There are a number of shades that will work quite well, but be sure that you have the hackle to match. Color as many shades as you feel you need for your geographic location. Felt tip pens work as well as anything. Once the colors are applied and thoroughly dried, coat them with tying cement (or 5 minute epoxy for a more durable shell). Give it a break and let them dry overnight. It never hurts to make up a bunch of these balsa couplets for future flies later in the season.
From this point, it's simple. Wrap a very short foundation in the middle of the shank. Tie down the balsa couplet, tie in the hackle, make a few turns and tie off. Trim the hackle top and bottom so that the sides are prominent and sits on the water with a low profile. The balsa does most of the floating, so the hackle doesn't need to be superior grade neck. (But don't get too soft, or the effect the hackle gives to the fly on the water is lost.)
As with most terrestrials, the best time to fish them for selective species of fish is right after a rain or on a windy day, when the forces of nature carry the little critters onto the water. In case of rain, avoid silt stained water as much as possible while casting. These are generally best fished near shoreline objects, like stumps, logs, low overhanging branches, anywhere large ants often come to the shore to drink or hunt food. Generally no action need be imparted. In still water, just let it sit and let the elements of nature supply all the animation necessary to the hackle. In a stream, just let it scoot along on its own, avoiding any drag over the target zone. Be patient and give the fish a chance to respond. As a rule, a floating ant isn't going anywhere in a hurry, so the fish won't be in a hurry unless there's competition for food. Give the fish time to make up its mind, which it will certainly do with this fly.