Pale Morning Dun

One of the great hatches of the West,
Pale Morning Duns have everything going for them: Massive numbers that trigger
aggressive surface feeding; a presence on nearly all the waters of the west;
fussy enough to offer a challenge, but not so difficult as to be too
frustrating; and they occur during the summer months when fishing is at its most
pleasant.

This small, pale-yellow mayfly of the crawler group is often
referred to by its initials, PMD.  Despite the name, hatches can occur in the
morning, early afternoon, or evening.  It's not unusual to have both morning and
evening emergences on the same day.  The hatch season begins as early as April
and can last as late as September, depending on the stream.  This is often the
dominant hatch where and when it occurs.

I never go to the Big Thompson or Rocky
Mountain National Park without a full box of PMD’s.