1912] Ditmars: Feeding Habits of Serpents 231 



highly specialized Viperine snakes, they seize their prey and retain the 

 hold until its death. All of them are omni-carnivorous , feeding upon 

 mammals, birds, reptiles, batrachians and fish. The writer has ob- 

 served none of the species — not even very young examples of any — 

 to show interest in earthworms or like food; the food appears to be 

 quite restricted to forms of vertebrate life, the latter a condition 

 noted with all the observed species of the Viperidae. This broad 

 range of food renders Ancistrodon characteristic among all viperine 

 serpents. The food habits of Sistrurus appear significant when com- 

 pared with structural characters similar to Ancistrodon. The writer 

 believes Sistrurus to be a direct offshoot of Ancistrodon and on an 

 independent branch of development from the larger and more highly 

 specialized rattlesnakes, Crotalus. The species of Sistrurus feed as 

 readily upon frogs as they do upon small mammals and birds. A 

 peculiar trait is the disposition to retain the hold upon cold-blooded 

 prey while they strike warm-blooded creatures. We thus note two 

 habits in their feeding — that of the more primitive long-fanged snake 

 and of the highly specialized type. The same feeding habits are to 

 be noted among the New World species of Lachesis — except L. mutus. 

 Snakes of the L. lanceolatus, alternatus and neuwiedii type feed upon 

 mammals, birds and batrachians, and are inclined when nervous, 

 to merely strike the warm-blooded food while the cold-blooded prey 

 is seized and held until dead or swallowed while it is alive, Lachesis 

 mutus is an exception. The writer is not at all convinced as to the 

 correctness of including this unique form under the same generic 

 heading of the snakes formerly grouped under Trigonocephalus. Its 

 source of origin has apparently branched abruptly away frcm It at 

 group and represents the origin of Crotalus, with the immediately 

 related South American C. durissus and the geographical extension 

 and elaboration of species toward and into North America. From 

 repeated examinations of the intestinal contents of examples of 

 Lachesis mutus, it seems to feed altogether upon warm-blooded prey. 

 Adult captive examples cannot be induced to take food; Mr. R. R. 

 Mole, of Port-of -Spain induced a young example to take mice. With 

 the reasonable certainty that this fine reptile, by far the largest of all 

 Crotaline serpents confines its food to warm-blooded prey, we have a 

 habit rendering it unique among the species of the genus it stands as 

 a member. These feeding habits also tally with those of Crotalus', no 

 example of any of the species of which has been noted by the writer 

 to feed upon other than warm-blooded prey. The writer's notes on 



