Oh. II.] FORAGIXG AXIS. 17 



common, which are linked together in a series of gra- 

 dations from species to species. One of these features 

 is a spot of black feathers on the breast. In some 

 species this is edged with blue, in others, as in the 

 species mentioned above, these black feathers are nearly 

 obsolete, forming only a small black spot nearly hidden 

 amongst the rust-coloured feathers of the breast. 

 Characters such as these, very conspicuous in some 

 species, shading off in others through various gradations 

 to insignificance, if not extinction, are known by natural- 

 ists to occur in numerous genera ; and so far they have 

 only been explained on the supposition of the descent of 

 the different species from a common progenitor. 



As I returned to the boat, I crossed a column of the 

 army or foraging ants, many of them dragging along 

 the legs and mangled bodies of insects that they had 

 captured in their foray. I afterwards often encountered 

 these ants in the forests, and it may be convenient to 

 place together all the facts I learnt respecting them. 



ECITONS, OR FORAGING ANTS. The Ecitons, or forag- 

 ing ants, are very numerous throughout Central America. 

 Whilst the leaf- cutting ants are entirely vegetable feeders, 

 the foraging ants are hunters, and live solely on insects or 

 other prey; and it is a curious analogy that, like the 

 hunting races of mankind, they have to change their 

 hunting-grounds when one is exhausted, and move on to 

 another. In Nicaragua they are generally called " Army 

 Ants." One of the smaller species (Edton predator) 

 used occasionally to visit our house and swarm over the 

 floors and walls, searching every cranny, and driving out 



the cockroaches and spiders, many of which were caught, 



c 



