For permission to examine specimens in their care I am indebted to
Charles M. Bogert, American Museum of Natural History (AMNH); Doris
M. Cochran, United States National Museum (USNM); Jean Guibe, Museum
National d'Histoire Naturelle, Paris (MNHN); Robert F. Inger, Chicago
Natural History Museum (CNHM); Hobart M. Smith, University of Illinois
Museum of Natural History (UIMNH); Charles F. Walker, University of
Michigan Museum of Zoology (UMMZ). (Abbreviations of institutions
given above in parentheses are used throughout; the Museum of Natural
History, University of Kansas is abbreviated KU.)
For their willing assistance in the field I am grateful to Ann S.
Duellman, Dale L. Hoyt, and John Wellman. Permits for collecting in
Mexico were generously issued by the late Ing. Luis Macias Arellano,
Departamento de la Fauna Silvestre, Direccion General de Caza. The
drawings in figures 1 and 3 were executed by Gail Selfridge. This
research has been supported by the National Science Foundation (NSF
G-9827).