122 ANIMAL INTELLIGENCE. 



versed, for while these occupy the middle place the 

 soldiers and officers march on either side. These have 

 large heads armed with powerful jaws, and never take 

 part in carrying ; their function is to maintain order, act 

 as scouts, and attack prey. The habits of these ants 

 resemble most closely those of the blind Ecitons in that 

 they very frequently, and indeed generally, build covered 

 ways ; they do so apparently in order to protect themselves 

 from the heat of the African sun. Their line of march 

 is therefore marked by a continuous arch or tunnel, which 

 is always being constructed by the van of the column. 

 The structure is made of earth moulded together by 

 saliva, and is very quickly built. But it is only built in 

 places where the line of march is exposed to the sun- 

 light ; at night, or in the shadow of trees or long grass, it 

 is not made. If their camp is flooded by a tropical rain- 

 storm, the ants congregate in a close mass, with the 

 younger ants in the centre ; they thus form a floating 

 island. 



It is remarkable that ants of different hemispheres 

 should manifest so close a similarity with respect to all 

 these wonderful habits. The Chasseur ants of Trinidad, 

 and, according to Madame Merian, the ants of visitation 

 of Cayenne, also display habits of the same kind. 



General Intelligence of Various Species. 



Many of the foregoing facts display an astonishing de- 

 gree of intelligence as obtaining among ants ; for I think 

 that however much latitude we may be inclined to allow to 

 * blind instinct ' in the way of imitating actions elsewhere 

 due to conscious purpose, some at least of these foregoing 

 facts can only be fairly reconciled with the view that the 

 insects know what they are doing and why they are doing 

 it. But as I am myself well aware of the difficulty that 

 arises in all such cases of drawing the line between pur- 

 poseless instinct and purposive intelligence, I have thought 

 it desirable to reserve for this concluding division of the 

 present chapter several isolated facts which have been ob- 

 served among sundry species of ants, and which do not 



