CREATION BY EVOLUTION 



nurses use as weaving-shuttles. Throughout the East Indies, 

 Northern AustraHa, India, and equatorial Africa the "tree 

 ants" of the genus Oecophylla (Fig. 7) have attained great 

 proficiency in the art of thus using their larvae for spinning 

 adjacent leaves together (Fig. 8). A similar habit has also 

 been acquired by certain species belonging to two other 

 genera, Polyrhachis, in the tropics of the Old World, and 

 Camponotus, in central and northern South America. The 

 nests made by C. senex and C. jormicijonnis in the forests of 

 British Guiana, Panama, and Guatemala are extraordinarily 

 like those made by Oecophylla long'moda in the forests of the 

 Congo and by Oecophylla smaragdina in the jungles of India. 

 The structure as well as the behaviour of remotely related 

 species of ants has been similarly modified by convergent or 

 parallel evolution in response to identical environment. A 

 fine example is furnished by certain ants in which the head 

 is cylindrical, constructed like the cork of a bottle, with a 

 hard, roughened, truncated anterior surface, and used for 

 closing the circular orifice of the nest, which leads to gal- 

 leries excavated in sound wood or in hard soil. Species of 

 at least four different genera in different parts of the world 

 (Camponotus, Pheidole, Crematogaster, and Epopostrufna) 

 exhibit this identical form of head. A similar modification 

 of the head is seen in a number of worms, bees, beetles, toads, 

 and tree-frogs; and in certain spiders, beetles, caterpillars, 

 snakes, and armadillos the posterior end of the body is sim- 

 ilarly modified for use as a barricade for closing the burrows 

 in which they live and thus preventing the entrance of 

 enemies. 



A different modification is seen in certain ants that live 

 in the narrow pith-cavities of the twigs and smaller branches 

 of tropical shrubs and trees. In these insects the whole 

 body becomes very long and slender, or even thread-like, or 



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