Current knowledge and predictions on the crepuscular bee genus Ptiloglossa (Colletidae: Diphaglossinae)

Within the family Colletidae, the genera Caupolicana and Ptiloglossa are known for their matinal and late afternoon foraging activities. This is not a common trait as most bee species are usually active during warm daylight periods. Ptiloglossa is the central and most taxonomically diverse genus but it is inadequately circumscribed and defined, and the sexes are not properly associated. In preparation for a revision of the Ptiloglossa of the world, I am conducting a review of the current knowledge about the genus including the U.S. species. Because of their foraging activities these bees are incompletely studied behaviorly and are relatively uncommon in most museum collections outside of the American tropics. The genus is distributed from the southwestern coterminous United States to northern Argentina, but oddly appears absent from Chile. Ptiloglossa arizonensis and P. jonesi are the only species of the genus reported for U.S.  Nesting biology, floral visitation and foraging activities are the only studied aspects of both species since their description in 1946. I predict based on collecting and studies on available specimens a thorough study of specimens accumulated in the last 69 years and sampling in poorly collected areas will reveal additional undescribed species, especially in the northern Andean regions, the Amazon Basin, and southern Mexico.