HABITS 93 



are provided with such a contractile pupil, are far 

 from exclusively nocturnal, delighting to bask in the 

 sun, and pairing and feeding in the day-time. The 

 Boidse appear to be more nocturnal, but no snake is 

 known to be absolutely so, and the two species of 

 Coluber which have been found living in perfect 

 darkness in limestone caves in the Malay Peninsula 

 and China, where they feed chiefly on bats, occur 

 also outside the caves, and probably never breed in 

 them. 



It is often stated in books that the organs of 

 locomotion for the exceedingly elongate body of 

 snakes are the ribs, and these creatures have even 

 been compared to Centipedes. This statement is no 

 doubt true to a certain extent for slow locomotion 

 on uneven ground, when the ribs and the corre- 

 sponding ventral shields afford a point of support ; 

 but it does not account for the rapid movements, as 

 when a snake darts like an arrow in pursuit of its 

 prey or to escape from an enemy. Besides, the 

 winding motions are not different from those of a 

 Slow-worm or Glass-snake, in which, encased as they 

 are in a bony armour, the ribs cannot come into 

 play at all. The action of the muscles alone is quite 

 sufficient to account for the reptation of snakes, 

 without the ribs having to play an essential part. 



Not only the Cobras, but several harmless snakes, 

 are able to raise the anterior third of the body 

 vertically, when taking up a threatening attitude in 



