It wasn't a great year for Epithecas here, but I provided Nick (Thomas W.) Donnelly with several specimens. Nick is one of the premier odonatologists in the U.S., and a founding member of the Dragonfly Societies of the Americas. He works a lot on teasing out relationships between geographic races, subspecies, and populations of odonata that may in fact be new species or intergrades. He has a particular interest in Enallagma cyathigerum/vernale (Northern/"Vernal" Bluets), Sympetrum rubicundulum/internum/janae, (Ruby/Cherry-faced/Jane's Meadowhawks) Amphiagrion saucium/abbreviatum (Eastern/Western Red Damsels), and, Epithecas of various types.
The verdict is in: I had two cynosura males, one intermediate male, and a costalis female. Below, I provide a few photos I too, through the microscope of the terminal appendages of the female.
Reference diagrams from Needham, Westfall, and May (2000) of the undersides of female Epithecas (Tetragoneuria).
E. cynosura (Common Baskettail)
Below, a female Epitheca from Wayne Co., MI, 29 May 2006. Specimen in acetone several hours before photos taken. Female was quite fresh, and had tinted wing tips. Nick Donnellly confirms this is E. costalis.