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 then* 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 
6 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 al] 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 
