SUPPOSED USE OF A PASSWORD. 123 
straugers two were taken into the nest and fifty were 
thrown into the water. I think it most probable that 
even these two were subsequently brought out and 
treated like the rest. 
It is clear, therefore, that in these species, and I 
believe in most, if not all others, the ants of a com- 
munity all recognise one another. The whole question 
is full of difficulty. It occurred to me, however, that 
experiments with pupe might throw some light on 
the subject. Although all the communities are deadly 
enemies, still if larvee or pupz from one nest are trans- 
ferred to another, they are tended with apparently as 
much care as if they really belonged to the nest. In 
ant-warfare, though sex is no protection, the young are 
spared, at least when they belong to the same species. 
Moreover, though the habits of ants are greatly changed 
if they are taken away from their nest and kept with 
only a few friends, still, under such circumstances, they 
will carefully tend any young who may be confided to 
them. Now if the recognition were individual—if the 
ants knew any one of their comrades, as we know our 
friends, not only from strangers, but from one another 
—then young ants taken from the nest as pups and 
restored after they had come to maturity would not 
be recognised as friends. On the other hand, if the 
recognition were effected by means of some signal or 
password, then the pupz which were intrusted to ants 
from another nest would have the password, if any, of 
that nest; and not of their own. Hence in this case 
