I have found nothing about this species in the writing of anglers, but the scientific literature shows it to be the most widespread species in the Ephemerella genus, and the only one that spans more than one continent. It may have gone unnoticed for so long because it might not produce thick hatches, and the sporadic individuals could easily be mistaken for Hendricksons. Where & When
Regions:This species was first described in Europe, and has also been found in Asia and North America. I have collected them in Alaska and New York, and probably Wisconsin, although the ID on the Wisconsin specimens is less certain.
East, Midwest, WestTime Of Year (?):
Mid-June to early August
I found ready-to-hatch, definitive Ephemerella aurivillii nymphs near Fairbanks, Alaska, in mid-July. However, because this species is found across such a large geographic range, the emergence timing probably varies widely. They may go unnoticed in the East due to overlaps in timing with more abundant Ephemerella species.
Pictures of 21 Mayfly Specimens in the Species Ephemerella aurivillii:
Male Ephemerella aurivillii Mayfly Dun
View 14 PicturesThis is the most widespread species of Ephemerella, and also the most abundant in some places, but nobody I've talked to seemed to know what its duns looked like, and there were no pictures of its duns online or in any angling books. That mystery is solved with this male dun, which hatched from a definitively identified nymph. Ephemerella aurivillii Mayfly Nymph
View 5 PicturesClose examination under a microscope showed definite small tubercles (
Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.) on the back of this nymph.
A few (not all) of the abdominal tubercles on this Ephemerella needhami
nymph are circled. They are especially large in this species.
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