The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
Chironomid pupae range from under 1/8" to over 1 inch in length; the nickname "bomber" refers to the larger pupae. Phillip Rowley, BC & AB author of Fly Patterns for Stillwaters: A study of Trout, Entomology and Tying, page 11.