Common Names: White-winged sulphur
Scientific Name: genus Caenis
These tiny mayflies are similar to tricos but are not nearly as vital to western anglers. Still, massive hatches occur and can be locally important. Nymphs inhabit very slow water in streams, or the margins of lakes. Duns emerge just before dark and almost immediately molt into spinners.
Caenis rate a page on this website only because anglers sometimes encounter swarms of them and wonder,"Is that some kind of trico? Should I bother to tie on a fly to match it?" The answers are "no" and "probably not." On the other hand, if you are sure trout are taking the duns, tie on an imitation and give it a try. What have you got to lose?
NYMPH COLOR. Dark brown
DUN SIZE: 2-7 mm (1/16 to 1/4 in)
DUN COLOR. Wings--white. Body--whitish abdomen, dark thorax
SPINNER SIZE. 2-7 mm (1/16 to 1/4 in)
SPINNER COLOR. Wings--clear. Body--same as dun
OTHER CHARACTERISTICS. Dun and spinner--three tails, no hind wings.