THE TROPICAL FOREST 117 



true boas, they are non-poisonous, crushing their prey 

 by the weight of their coils. The huge anaconda 

 (Euneces murinus) of the Amazonian forests is semi- 

 aquatic, lurking in pools till its prey approaches the 

 water. It feeds largely on peccaries. The true boas 

 occur both in Madagascar and in tropical South America, 

 and inhabit the dense forests, through which they ban 

 ghde without difficulty. The beautifully coloured and 

 marked wood-snakes (Herpetodryas)of tropical America 

 represent there the tree snakes (Dendrophis) of the Old 

 World, all of which are arboreal in habit. The American 

 forms feed upon Hzards and young birds. In India the 

 very agile whip-snakes (Dryophis) twine their slender 

 bodies round branches of trees, shooting out their heads 

 in order to capture their prey. Most other snakes, includ- 

 ing the most poisonous forms, are ground animals, 

 often inhabiting dry and sandy places. An exception 

 is the climbing tree-viper (Trimeresurus gramineus) of 

 India and Burma, with a markedly prehensile tail, and 

 a generally green tint, Uke the trees among which 

 it hves. 



Of the amphibians we have already mentioned the 

 flying frogs of the genus Rhacophorus, which occur in 

 Madagascar, and also throughout South-East Asia. 

 A number of other frogs show more or less well-marked 

 arboreal habits, the commonest adaptation being the 

 development of some form of adhesive disks at the end 

 of the toes, to permit of the animals fixing themselves 

 to the branches of trees. This is seen in the family of 

 Dendrobatinae, whose members occur alike in Mada- 

 gascar and in tropical America. They are beautifully 

 and often vividly coloured, and some species at least 

 have poison glands in the skin, whose secretion is used 

 in South America as an arrow poison. Such an associa- 



