Mayfly Species Paraleptophlebia packii (Mahogany Dun)

This large western species is common in places. It is one of the few that has tusks and substitutes for the more common tusked Paraleptophlebia bicornuta in some locales, particularly the central Rockies in parts of Colorado, Utah, and Wyoming where they have been documented. Telling the tusked species apart is very difficult and even entomological texts are largely ambiguous on the characters that differentiate the nymphs. Angling texts relying on gill morphology, terga pattern, and tusk shape are dubious at best. For now, the angler's best bet is to rely somewhat on documented distribution.