SPECIAL PRECAUTIONARY HABITS 327 



terrestrial forms of this interesting family, which abound in 

 England and temperate countries generally, are scarce in the 

 neighbourhood of Para; in fact I only met with four or five 

 species. On the other hand, the purely arboreal kinds were 

 rather numerous. The contrary of this happens in northern 

 latitudes, where the great majority of the species and genera 

 are exclusively terrestrial. . . . The remarkable scarcity of 

 ground -beedes is doubdess attributable to the number of ants 

 and termites which people every inch of surface in all shady 

 places, and which would most likely destroy the larvae of 

 Coleoptera." 



Some of the members of certain ancient groups now on the 

 decline have taken to an arboreal life, trees affording them a 

 refuge which at the same time yields an abundance of food. 

 Such, for example, are the defenceless leaf-eating Sloths, crea- 

 tures of comparatively small size, which are remarkably special- 

 ized in structure to fit them for their life among the trees of the 

 South American forests. The explanation here suggested is sup- 

 ported by the fact that tree-dwelling sloths are a young group, 

 geologically speaking, and find their nearest allies among extinct 

 forms in the Ground-Sloths, which, though they appear to have 

 lived on foliage, were quite unable to climb. Some of these 

 creatures attained a very large size, Megatherium, for example, 

 rivalling the elephant in that respect. The Neomylodon of Pata- 

 gonia, perhaps even yet living, is, or was, a similar kind of 

 animal. 



Parachute Animals. — Certain climbing forms have developed 

 folds of skin converting them into what may be termed "parachute 

 animals", an arrangement which facilitates progress from one tree 

 to another, and is protective in so far as it may be supposed to 

 facilitate escape from enemies. Such among mammals are Flying 

 Squirrels, while lizards present the case of Flying Dragons, and 

 Flying Frogs are found among amphibians. From this kind of 

 apology for flight we naturally pass to flying animals proper. 



Flying Animals. — The geological record proves that Insects 

 led the way in the conquest of the air, thereby vastly facilitating 

 their progress from place to place in pursuit of prey, and affording 

 more or less protection by thwarting many of the attacks of wing- 

 less enemies. And it is noteworthy that the oldest known insects 

 find their nearest allies among recent Orthoptera of the cockroach 



