1912] Ditmars: Feeding Habits oj Serpents 219 



ally feeds upon other snakes and lizards, but seldom can be induced 

 to feed upon frogs. These habits relate generally to the different 

 species of Zaocys and Zamenis, some having a wider range of diet 

 than others, a few feeding almost entirely upon lizards and other 

 small snakes. 



Before considering the feeding habits of the other genera men- 

 tioned, it is of significance to state that among the species of the 

 subfamily Coluhrinae, the tendency is for the viviparous species to 

 subsist upon cold-blooded prey, while the great majority of the ovi- 

 parous species subsist upon warm-blooded animals, or a mixed diet 

 of warm and cold-blooded creatures. All of the species in the present ' 

 group of genera are oviparous. 



Salvador a and Phyllorhynchus are apparently off -shoot genera 

 from the Zamenis type'. Their distribution involves dry and arid 

 regions, and we note the food of Salvadora to consist of lizards 

 and small rodents. The feeding habits of Phyllorhynchus are prac- 

 tically unknown, but judging from structure, it apparently feeds 

 upon small lizards, other snakes and possibly the young of the smaller 

 rodents. Drymohius is a genus of the warmer latitudes and its 

 members feed largely upon batrachians, lizards, and occasionally 

 although not frequently, upon small mammals and young birds. 

 Spilotes stands intermediate in relationship between Zamenis and 

 Coluber, two important genera with a considerable number of appar- 

 ently related forms. The species of Spilotes are particularly inter- 

 esting in their feeding habits, as they are quite omni-carnivorous — 

 feeding upon lizards and snakes, all types of batrachians, includirg 

 the toads, which lack of preference in the selection of prey am.ong 

 creatures that greatly vary in a possession of highly irritating skin 

 secretions, is quite unusual for serpents that also prey as often as 

 occasion permits, upon mammals and birds. The species of Spilotes 

 must be regarded as of considerable economic value, as mature 

 examples are bold hunters and ever on the alert for rats and mice. 

 Highly active, they feed more frequently than many serpents, and 

 while noting this trait, it is of importance to state that the feeding 

 intervals of various serpents are positively governed by the char- 

 acteristic activity or inactivity of the reptiles involved. As exam- 

 ples of the inactive type the writer quotes the members of the Boidae, 

 which if fed at intervals of twenty days apart will remain well 

 nourished, while serpents of the type represented by Spilotes, 



