THE TROPICAL FOREST 117 
true boas, they are non-poisonous, crushing their prey 
by the weight of their coils. The huge anaconda 
(Huneces 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 can 
glide 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 lizards 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 (7'rimeresurus gramineus) of 
India and Burma, with a markedly prehensile tail, and 
a generally green tint, like the trees among which 
it lives. 
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- 
