The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
At least for the size fish I'm most interested in... :)
(my interest) (trout) preferably at least 18", that stick their noses out, or boil on, aquatic insects.
BTW I'm responding at 1:15 a.m. because I'm all wired about leaving for Montana in about five hours for two weeks of great hatches and big rising wild trout. :)