1912] Ditmars: Feeding Habits of Serpents 201 



exhibit power of constriction, and this is also to be noted among the 

 crude and lowly serpents of ancient lineage, such as the Typhlopidae 

 and Glauconiidae, but as all of these creatures are mainly insectivor- 

 ous the power seems of no practical value. Constriction, as an effi- 

 cient and unvarying method of killing the prey has apparently orig- 

 inated among the members of the Boidae, the ancient lineage of 

 which serpents is evident by the presence of rudimentary hind limbs. 

 During the process of specialization it has been retained by many 

 members of the .Coluhridae, particularly those that feed upon warm 

 blooded prey, and curiously enough a strong indication of it here and 

 there appears among highly specialized forms, with well developed 

 fangs. Intermediate traits have already been noted among the Colu- 

 brine semi-constrictors and those species which swallow the prey 

 alive. 



It is of interest in continuing this preliminary resume to note the 

 relationship of food to the methods of feeding. The following table 

 will concisely outline such observations: 



NON-VENOMOUS 



Constrictors* : Series a. Species that feed only upon warm- 

 blooded prey— mammals and birds. The greater number of 

 the species of the Boidae. Many genera of the Coluhridae — 

 of which the members of Coluber are typical examples. 

 Series b. Species that feed upon warm and cold-blooJed prey. 

 These snakes devour mammals, birds and other reptiles, 

 though few or none feed upon batrachians. Members of the 

 Boidae and Coluhridae. 



Semi-Constrictors: Omni-carnivorous serpents feeding largely 

 upon mammals and birds, but also reptiles and batrachians. 

 Principally Colubrine snakes. 



Non-Constrictors: The great majority of these species devour 

 cold-blooded creatures — other reptiles, batrachians, fishes 

 and insects. A large number of Colubrine genera come under 



*The greater percentage of the food of constricting species consists of 

 warm-blooded animals. 



