Ephemera guttulata's size, numbers, and hatching characteristics have made it a favorite of fly fishermen since the sport first came to North American waters.
It is on par with the Midwest's Hexagenia limbata hatch for its ability to lure huge piscivorous brown trout to eat insects at the surface once a year. The special charm of the Green Drake hatch is that it often takes place during pleasant spring afternoons. It can be challenging because the large flies are easy for trout to inspect in the daylight and they feed very selectively, especially late in the hatch. The huge difference in appearance between green drake duns and the spinners, white-bodied "coffin flies," makes them a peculiarity among major hatches.
The Green Drakes are on the decline due to environmental degradation.
Beardius on Aug 1, 2008August 1st, 2008, 7:16 am EDT
Emergence periods for green drakes usually run for 7-10 days in most streams. However, there are streams in the east where emergence periods are prolonged by some of the nymphs being parasitized by Nanocladius and Epoicocladius midge larvae. In these streams, emergence may be prolonged to 21 days. Unparasitized nymphs emerge before parasitized nymphs, with each group showing separate peaks of emergence about a week apart. This is based upon my own research on green drake emergence in streams with these midge species.
My question here is this: does anybody know of streams that have this type of prolonged emergence (2-3 weeks) in NY, PA, MD, or WV?
Wbranch on Aug 3, 2008August 3rd, 2008, 1:05 am EDT
Yes, the WB of the Delaware in NY has a prolonged emergence period not only for guttalata but for many mayflies. I will see Ep varia on the lower end of the WB by the third week of April and will see them still emerging near the reservoir by May 15 with a spinner fall the next week.
I often see Green Drakes emerging by my cabin on the lower WB by May 20 - 23 then when the hatch is over on the lower river I will see them in Deposit or the upper East Branch almost to the middle of June.
Beardius on Dec 4, 2008December 4th, 2008, 7:16 pm EST
That fits with what I would expect for a stream that does NOT have these parasitic midges. If they were present, the emergence would last at least 2 weeks, with the first week seeing emergence of unparasitized mayflies, and the remainder being mayflies that had been parasitized.