When there are bugs on the water, it’s pretty easy to figure out what’s hatching. All you have to do is collect a few insects, note their size, color, and silhouette, and then tie on your best-matching pattern. But, as we all know, you can’t count on duns floating by at all times. In these situations, you have to look elsewhere for evidence. Where, you ask?
Start with streamside vegetation. Most species of aquatic insects stick close to home in the time between hatching and when they return as spinners or ovipositors. Sometimes, the insects will be quite evident, clustered on blades of grass and bushes. If you can’t see the bugs, shake some bushes and see what flies out. You’ll often be amazed at how many insects were in that “bugless” shrubbery you just examined.
Next, inspect the surface of any eddies, sloughs, or floating foam to see what has collected there. Stillborn duns or last night’s spinners might still be visible.
Other great places to find evidence include streamside spider webs, the screens of nearby buildings, and the front grilles of the cars in the parking lot at the fishing access. Even a smashed mayfly can offer clues to what size and color you should use.
If stoneflies are hatching, you’ll find their shucks on the rocks in the stream itself. If you root around enough in these places, or anywhere else you’d expect bugs to congregate, you can get a good idea what hatched yesterday. And if it hatched yesterday, it’ll more than likely hatch again today.
Finally, you could swallow your pride and just ask another angler, if any are around. In our culture, this is often frowned upon, but it can be very effective. And most fly fishermen are perfectly willing to help a stranger.