The transformation of the nymphs to the adult stage occurs in July and August and is quite fast. In fact, this large mayfly has one of the shortest adult stages.
A tandem rig proves useful when fishing the White Miller hatch. This rig consists of a #14 tan nymph on the tippet, with a # 16 White Fly spinner further up the line. This is meant to imitate the male coming to fertilize the female. Hatches occur swiftly and can be very heavy. The most success is met early in the hatch, since fish feed so voraciously at the start that they become engorged and stop feeding before the hatch is over.