Abstract
Factors, i.e., time, climate, and isolation, that have or may possibly have influenced the distribution and speciation of Scarabaeidae in North America are discussed. Specific examples of present distributional patterns in the genera Phyllophaga, Serica, Diplotaxis, Onthophagus, Geotrupes and Trox are mapped and described. A general comparison of the distributional patterns is made, and inferences are drawn concerning centers of dispersal and (or) areas of survival of the insect inhabitants of deserts and temperate forests during the various climatic changes of the Pleistocene.