182 ANIMAL COLOEATIOK. 



One of the pelagic sea snakes belonging to the genus 

 Hydrophis * is similarly ringed with black and yellow ; these 

 slender serpents, which often grow to a considerable lengthy 

 are extremely poisonous, but not generally so conspicuously 

 coloiired. On the other hand, the common English viper, 

 the Puff adder, the Fer de lance, and the Eattlesnake are 

 rather protectively coloured, if anything ; and the accounts of 

 travellers aboimd with instances of the narrow escapes they 

 have had from the invisibility of these reptiles. Mr. Salvin 

 has described a green tree-viper from Guatemala.! Warning 

 colours in snakes, as in other animals, have not been brought 

 about to assist them in impressing human beings with their 

 venomous nature ; they have to contend with much more 

 important foes than our own species, but these cannot be saiid 

 to be very numerous. 



There are a few snake-eating birds, such as the Secretary 

 bird and that large Australian kingfisher called the Laughing 

 Jackass. The Ground hornbill of Africa will also eat serpents. 

 Among mammals the mongoose is an enemy to snakes, and 

 swine are said to be impervious to the poison of the rattle- 

 snake and other venomous serpents, which they will kill and 

 devour ; but their immunity from the effects of the venom has 

 been denied. In India the formidable Opluophagus lives, as 

 its name denotes, upon snakes ; and it will kill and eat a 

 cobra with perfect indifference. 



There does not, therefore, seem to be so much need for 

 warning colours among poisonous snakes as in other groups : 

 snake-eating animals seem to disregard the bite of the snake, 

 either because it produces little or no effect upon them, or 

 because they possess special means of defence against the bite; 



* See Trans. Zool. Soc, vol. II., Plate 5(;. 

 t Proc. Zool. Soc, 1860, p. 457. 



