Emerger flies are easy to use, and they catch fish. Here’s what you need to know

It’s a frustrating and baffling situation, and we’ve all been there. Insects are fluttering on and around the river, but the trout are ignoring them—not to mention your dry fly—and rising to some other seemingly invisible food. Or similarly, you might see the gentle swirls of rising fish, but there’s no apparent sign of insect activity. What the heck is going on? The answer is an often-overlooked part of a trout’s diet: emergers. Here’s a primer on these essential flies.