ANTS. 59 
anxious for the good of the colony, to the same extent as 
the former denizens of the place. From this, as a 
starting-point, has gradually developed one of the most 
remarkable of the habits acquired by certain species of ants 
—for they do not all do it—that of “slave-making.” In 
the case of some species of ants the practice has been carried 
out so long, and to such an extent, that the “masters” are 
entirely dependent upon their “ slaves ”—being, indeed, too 
indolent even to feed themselves. Formica sanguinea is the 
only British species of slave-making ant, and, let us Britons 
be thankful for it, this ant can and does quite commonly 
do without slaves at all. Its “slaves” are Formica fusca, 
F. cunicularia, and Lasius flavus. The ant just referred to as 
helpless without its “ slaves” is Polyergus rufescens, 
In the case of a large colony of ants it might be expected 
that there would be a further division of labour than 
happens in the case where the duties of the citizens have to 
be performed by only afew. Accordingly, we find that some 
species of ants have gradually evolved more than the three 
forms hitherto referred to as the queen, the male, and the 
worker. The evolution, as might be expected, starts by a 
modification of the last-named form. One curious modifica- 
tion arises from the need of having part of the community 
told off for what may be termed police duty. This has led 
to the gradual evolution of a special form of ant, which does 
not appear to perform many of the duties carried out by the 
rest of the colony. Another modification has started from 
military requirements, which have resulted in the evolution 
of a race of ants who are of not much use for anything but 
fighting. They can bite and sting wonderfully well; but 
they are, so to speak, simply of no use at all as nurses, or 
housekeepers, or masons, or shepherds, or purveyors, or any 
one of the other multifarious duties that fall to the lot of 
the other members of the ant community. 
Then another line of modification has had its origin in 
the need for some one to attend to the meals while the rest 
of the community are otherwise engaged. Even amongst the 
commoner species of ants, certain individual workers, 
apparently in no way different from the rest, are told off to 
