Z, many thanks! Busck does not describe the host plant; are the host plants for both species the same? Powell and Opler (2009) describe the FW of Ypsolopha maculatella (which they confusingly alternately label Y. maculatana in some photos) as "variable...from distinctly and intricately patterned with gray brown to nearly all white" but mention that the host plant of this species is Ephedra (where I saw this moth) and that the moth can be found on its host plant in the Owens Valley (where I found the moth) in May (this photograph was taken in early June, but the moths first emerged in May). I found a moth of similar structure but with vastly different wing markings

as well as several similar moths but without sharply defined maculations or darker brown scales on the FW (which I didn't post photos of because they were so similar to then-current BG photos of Y. maculatella) on the same Ephedra at approximately the same time of day. Hence my conundrum: Are the moths one species with highly variable wing markings (matching historical descriptions of more than one species) using the same host plant at the same time of year, or are the moths different, closely related species using the same host plant at the same time of year?