88 TROPICAL NATURE, AND OTHER ESSAYS. 



flocks of insectivorous birds who prey upon the winged 

 insects that are continually trying to escape from the 

 ants. They even attack wasps' nests, which they cut to 

 pieces and then drag out the larvae. They bite and sting 

 severely, and the traveller who accidentally steps into a 

 horde of them will soon be overrun, and must make his 

 escape as quickly as possible. They do not confine 

 themselves to the ground, but swarm up bushes and low 

 trees, hunting every branch, and clearing them of all 

 insect life. Sometimes a band will enter a house, like 

 the driver ants in Africa, and clear it of cockroaches, 

 spiders, centipedes, and other insects. They seem to 

 have no permanent abode and to be ever wandering 

 about in search of prey, but they make temporary habi- 

 tations in hollow trees or other suitable places. 



Perhaps the most extraordinary of all ants are the 

 blind species of Eciton discovered by Mr. Bates, which 

 construct a covered way or tunnel as they march along. 

 On coming near a rotten log, or any other favourable 

 hunting ground, they pour into all its crevices in search 

 of booty, their covered way serving as a protection to 

 retire to in case of danger. These creatures, of which 

 two species are known, are absolutely without eyes ; and 

 it seems almost impossible to imagine that the loss of 

 so important a sense-organ can be otherwise than in- 

 jurious to them. Yet on the theory of natural selection 

 the successive variations by which the eyes were reduced 

 and ultimately lost must all have been useful. It ia 

 true they do manage to exist without eyes ; but that is 

 probably because, as sight became more and more imper- 

 fect, new instincts or new protective modifications were 

 developed to supply its place, and this does not in any 



