This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
Konchu on Nov 28, 2012November 28th, 2012, 4:10 am EST
Jason can boot this if he wants, because it's kind of an advertisement, but I thought a few of the die-hard bug aficionados might be interested. I'm planning to give a workshop on western (north of Mexico) and far northern North American mayfly nymphs. It will be January 3-5, in Long Beach, California, USA. There is a price tag for participation (that I did not set). See the following link for more details, or send me a PM. This will be a fairly advanced and intensive event. I'll cover most topics at the species-level. Notably, a bunch of new regional and comprehensive identification keys will be debuted. This includes the first keys for several genera, greatly revised keys for others and the first discussions of some undescribed nymphs. Emphasis will be placed on the families Baetidae, Heptageniidae, Ephemerellidae, Leptophlebiidae and Leptohyphidae. Other contributors include Nick Wiersema (wrote keys) and Jeff Webb (wrote keys and will attend). Please feel free to share this information elsewhere, but please send me a PM first.