84 A NATURALIST IN BORNEO 



to its surroundings this specimen was bright ochreous 

 except the tail, which was of the usual brown colour. 

 On bottling the specimen in formalin I was surprised 

 to see that the ochreous colour very soon turned into 

 the bright grass-green of the tree- and shrub-haunting 

 form. From this observation it is quite obvious that 

 this species has considerable powers of altering its 

 colour to suit its surroundings ; its usual habitat is 

 arboreal, and the green colour is the more primitive. 

 In response to a change of environment the snake can 

 alter its colouring, but sudden death destroys the 

 mechanism whereby this change is brought about, and 

 the snake in death reverts to the primitive colouring of 

 the species [Note 8, p. 314]. 



Another species of the same genus, Coluber tceniiirns, 

 is found in limestone districts amongst rocks, and its 

 mottled colouring harmonizes wonderfully well with 

 the limestone and the lights and shadows produced 

 by overhanging foliage. Mr. H. N. Ridley obtained 

 specimens inside quite dark caves in the Malay Penin- 

 sula, and found them very much paler than specimens 

 caught outside the caves in fact, almost white. These 

 cave-dwellers lived on the bats that thronged about 

 them. The two last-named species are then charac- 

 teristic protectively coloured snakes, but their congener, 

 C. melanurus, though not a very conspicuous species, 

 does not rely so much on its resemblance to its sur- 

 roundings to protect it as on a very aggressive attitude 

 that it adopts when irritated. It is rather a savage 

 snake ; when it is teased it raises the front third of 

 the body just slightly off the ground, throws this part 

 into a series of S-shaped curves, and hisses threaten- 

 ingly. In this attitude the front part, at least, of the 



