HARVESTING ANTS. 161 



riffht to the habit of harvestino^, for it is clear that a 

 given tract of country can only afford supplies of 

 grain to a limited number of colonies ; so that, if 

 these ants have taken up the ground and are strong 

 enough to maintain possession, no others would have 

 a chance. However this may be, I find that the 

 more insight I gain into the distinctive habits and 

 relations of animals, the more the belief impresses 

 itself upon me that wherever we find many closely- 

 allied species inhabiting restricted areas, there we 

 may safely look for important differences among these 

 species in respect of their modes of life, and in the 

 development of their instinct and intelligence. And 

 indeed this may be considered as a corollary of the 

 great law of natural selection, which uniforml}- tends 

 to secure the greatest possible amount of divergence 

 in this respect, and to prevent the co-existence in close 

 proximity to each other of distinct species having the 

 same requirements and manner of life. 



Thus, for example, even Atta barbara and striictor, 

 though most closely related as species, differ in habit ; 

 the former leading a much more active life during 

 the winter months at Mentone than the latter, and 

 seeking its home rather in wild than cultivated ground. 

 Then what difierences different ants present in re- 

 spect of strength, speed, powers of offence and defence, 

 numerical strength of colonies, timidity, date and 

 frequency of departure of winged ants from the nest, 

 odour emitted, combativeness, architecture and selec- 

 tion of localities, nature of food, nocturnal and 

 diurnal habits, and in many other properties and con- 

 ditions ! It is doubtless owing to dissimilarity in 

 these and other respects that it becomes possible for 



