Tips on Terrestrials
If you think terrestrial imitations are only for summer fishing, you're missing the boat. I've caught trout from early spring through November on terrestrials.
Numerous studies of trout stomach contents have shown that land-based
insects are a dominant trout food not only in August, but also in May,
June, and September. Well into October and November, beetles can be the
most abundant food in a trout's stomach.
| If you fish small streams, terrestrials are
even more important than in larger rivers. A trout's diet in such places
is made up almost entirely of terrestrials because these smaller waters
don't have large expanses of insect-producing riffles. I suspect this is
the reason why "attractor" flies are so effective.
Unlike fish responding to a hatch, trout can be eating terrestrials and you'll never notice. When trout eat low-floating terrestrial insects, there is hardly ever a splash. Sometimes you see a subtle ring on the water, sometimes a snout poking above the surface, and sometimes you see a hopper just disappear into a hole in the water.
The best places to try your offering are where riffles deepen into a dark slot (especially near a deep bank but not necessarily), in concave impressions along a bank that form small bays, and along undercut banks, especially ones that flow through meadows.
Here are a few thoughts on the subject