326 ANIMAL DEFENCES 



are to be seen. A genus of Plantigrade Carnivora, allied to the 

 bears {Cercoleptes), found only in the Amazonian forests, is entirely- 

 arboreal, and has a long flexible tail like that of certain monkeys. 

 Many other similar instances could be enumerated, but I will 

 mention only the Geodephaga, or carnivorous ground beetles, a 

 great proportion of whose genera and species in these forest 

 regions are, by the structure of their feet, fitted to live exclu- 

 sively on the branches and leaves of trees. . . . The largest and 

 most interesting portion of the Brazilian mammal fauna is arboreal 

 in its habits; this feature of the animal denizens of these forests 

 I have already alluded to. The most intensely arboreal animals 

 in the world are the South American monkeys of the family 

 Cebidae, many of which have a fifth hand for climbing in their 

 prehensile tails, adapted for this function by their strong muscular 

 development, and the naked palms under their tips. This seems 

 to teach us that the South American fauna has been slowly 

 adapted to a forest life, and therefore that extensive forests must 

 have always existed since the region was first peopled by mam- 

 malia." Enough has been said to show that food-supply alone 

 must have had a great deal to do with the evolution of arboreal 

 forms, and it would be easy to draw up a number of cases on the 

 model of The House that Jack Built to illustrate chains of causes 

 and effects that have arisen as a result. Trees have produced 

 fruits and seeds, fruits and seeds have led to the evolution of 

 fruit- and seed-eating monkeys, &c., fruit- and seed-eating monkeys, 

 &c., have led to the specialization of climbing carnivores. Simi- 

 larly the wood and bark of trees have afforded nutriment to 

 various insects, and this has resulted in the evolution of wood- 

 peckers and other arboreal insectivorous forms. 



All this may be the truth, and nothing but the truth, but it is 

 by no means the whole truth. It is practically certain that some 

 animals have taken to feed among trees, not merely for the sake 

 of the aliment there present, but also in order to avoid enemies 

 living upon the ground. In such cases the arboreal habit is partly 

 a protective measure. Why, for example, should the carnivorous 

 ground-beetles of the Amazon forests have taken to live among 

 the trees, as stated by Bates in the extract given above? A 

 possible solution to this is given by the same zoologist elsewhere. 

 "It is vain to look for the Geodephaga, or carnivorous beetles, 

 under stones, or anywhere, indeed, in open, sunny places. The 



