What’s a PMD?

Well, entomologists used to split this species into Ephemerella Inermis and Ephemerella Infrequens, but now they are much easier to identify as they are all Ephemerella Excrucians. Anglers just call them PMDs.  PMD stands for Pale Morning Dun. But of course they sometimes hatch in the afternoon or evening.  In the simplest terms, PMDs are one of them pretty little Mayflies that trout like to eat.

PMD’s are pretty important, in that they hatch on many western waters from June to September.  On the Missouri, they typically come on strong in early June and last well into August. Fish will take the nymphs, the emergers, the cripples, the duns and the spinners.  The well-known Rusty Spinner is a classic PMD pattern.  Hook sizes to match the naturals range from 14# to 18#, with #16 being the most common.