The examination of museum specimens allows for the robust analysis of ecological and life history traits in snakes, and can be especially useful in revealing characteristics often undetected in geographically limited studies. We measured and dissected 242 Psammophis crucifer and 358 Psammophylax r. rhombeatus, two widespread and abundant psammophiids from southern Africa, and quantified sexual size dimorphism (SSD), feeding habits, and geographic variation of these traits throughout their range. Female P. crucifer and male P. r. rhombeatus were larger than the opposite sex, both species were saurophagous but P. r. rhombeatus incorporated a wider range of taxa, and the reproductive biologies of both species were consistent with those of their congeners. We also examined intraspecific variation in these ecological traits based on differences in annual and seasonal rainfall patterns across their broad distribution. In large part the ecology of these temperate-inhabiting snakes mirrors that of other psammophiids and convergent whipsnakes.