The smallest terrestrial can make a big difference in August.
Trout and ants are like kids and candy. No matter what the main menu has been, trout are almost invariably suckers for a favorite sweet. Ants are an intermittent food supply all season but become especially important in the low water of late summer and early fall. That’s because seasonal hatches of most aquatic insects are over, and terrestrial insects that fall on the water-including ants, grasshoppers, crickets, and beetles-become proportionately more important in the trout’s diet. Among those, ants are often most prevalent.
Ants are most active in the heat of the day; cool mornings and evenings are the wrong times to be fishing such patterns. The slow sipping rises of summer-afternoon trout often betray ant feeders. At other times, a massive rise of trout with no apparent insect hatch can mean that flying-ant swarms have fallen to the river’s surface. Here’s how to fish both situations.
If you watch a trout pool during the late morning and afternoon, you’ll often see the occasional gentle dimple of a rising trout. These rises will often be near a pool’s center where the main current tongue slows and spreads. Such rises tend to be subtle and irregular, and they usually indicate trout rising to random terrestrials trapped in the current.
These fish can be tough to take. The late-season water is low and clear, and the trout themselves are well educated, having already seen thousands of artificials during the spring and early summer. Such fish will usually take a very small ant pattern fished dry. I typically start with a size 20 Black or Cinnamon Fur Ant fished on a 6X tippet, but you can also try a foam or carpenter ant.
If the river is large enough, fish down and across with a slack-line dry-fly cast to the trout. This means that the fly floating downstream will drift into the fish’s view before the leader. It’s imperative there be no drag on the fly. To avoid it, feed slack line into the downstream drift a little at a time by shaking your rod tip gently. If the fish doesn’t take, allow the current to swing the line, leader, and fly well away from it before you pick up for another cast. On smaller streams, where there isn’t enough room for down-and-across fishing, you’ll have to work upstream. Remember to keep a low profile-on your knees, if necessary-and to keep your false casting off to the side and away from the trout’s view.
From mid-August through September, trout rivers nationwide are occasionally blitzed by swarms of flying ants. This usually takes place in the afternoon, when thousands of winged ants fall to the surface almost simultaneously. The swarms themselves are the mechanism by which ant colonies that grew over the summer disperse and have nothing to do with the river itself. The ants just happen to fall there. Such swarming is most apt to occur on a warm, humid afternoon with little wind that in turn occurs 24 hours after at least a moderate rainfall. To that extent, ant swarms are somewhat predictable. The sudden appearance of so many insects often triggers an incredible rise of trout.
Unfortunately, because the insects in a swarm are uniform, the trout also become maddeningly selective. In general, the ants will be black, brown, or cinnamon in color, ranging in size from about 14 down to 24. If your patterns are off in either size or color, you’re in for a very frustrating experience. But once you’re dialed in to the action, it could be the sweetest fishing afternoon you’ve had in years.