Extracted from P. H. Timberlake. A Revisional Study of the Bees of the Genus Perdita F. Smith, with Special Reference to the Fauna of the Pacific Coast ( Hymenoptera, Apoidea Part V). University of California Press Berkeley and Los Angeles 1962|
This species is closely allied to dasylirii and the males of the two species are rather difficult to distinguish, but the female of polytropica has the mesonotnm uniformly dark green and tessellate, and duller than in dasylirii. The male has the mesonotum also duller and clothed with coarser, more conspicuous, but sparse white hair. The two species fly together in some localities in Arizona and both have been taken on the same day in Sabino Canyon, Santa Catalina Mountains, where they were probably visiting the same flowers. I have divided polytropica into two subspecies: the light markings of face and abdomen are distinct in the typical form, but are usually absent or more or less evanescent in obsoleta.