Ants are one of the best-known terrestrial food sources for trout. Wingless ants often stumble by accident into the water, making them a very common "occasional" item on the trout's menu. Imitations of these unlucky critters make excellent searching patterns in mid- to late summer.
The real fun with ants, however, comes from the mating swarms of winged species. They are spotty and hard to predict, but when they happen to fall over the water they can draw more trout activity than all but the best hatches of huge mayflies.
Formicidae Fly Fishing Tips
Ant imitations are effective above and below the surface.
A heavy fall of ants will make trout extremely selective to their distinct form, and smoothly tapered mayfly imitations in the correct size and color are likely to be rejected on account of their shape.
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I collected this flying ant from the surface of a popular Catskill trout stream, where its species prompted steady rising from selective trout for several late-morning hours. It was mixed with smaller ants of a different color, and I photographed one of them too.
An ant struggles to escape the surface of a Catskill stream. The black dot on the right is the ant's shadow on a rock on the bottom. I can see how this would appeal to a trout. Even I kind of want to eat the thing.
Flying ants were falling very thick on the water during a beautiful Montana evening in August. They were collected in great numbers in this eddy, which made it difficult to entice a trout with a fly amidst all the naturals, but a few nice browns were fooled.