Louse-Host Associations of Geomydoecus (Mallophaga: Trichodectidae) with the Yellow-Faced Pocket Gopher, Pappogeomys Castanops (Rodentia: Geomyidae)1

The distribution of 6 taxa of lice of the genus Geomydoecus on Pappogeomys castanops appears to divide the hosts into northern and southern subspecies-groups. The northern subspecies-group of P. castanops has G. expansus and 3 morphologically similar lice of the texanus-complex, but lacks G. subnubili and G. martini. The southern group has G. subnubili, usually with G. martini or occasionally with G. expansus on the same host, but without G. expansus alone. Principal components analysis indicates that the northern and southern populations of G. expansus show slight morphological differences from which we infer isolation.