Wasps, Bees, and Ants 
557 
Darwin says: “The case (of ant communities with worker castes) also is 
very interesting, as it proves that with animals, as. with plants, any amount 
of modification may be effected by the accumulation of numerous, slight,, 
spontaneous variations, which are in any way profitable, without exercise 
or habit having been brought into play. For peculiar habits, confined 
to the workers of sterile females, however long they might be followed, could 
not possibly affect the males and fertile females, which alone leave descend¬ 
ants. I am surprised that no one has hitherto advanced this demonstrative 
case of neuter insects against the well-known doctrine of inherited habit as 
advanced by Lamarck.” 
It will be noted that the answer to the first question as to how the marked 
differences between the fertile and the sterile forms of ants in any nest are 
brought about during individual development, and the answer of Darwin 
to the second question as to how these differences have been brought about 
in the species itself, are not thoroughly in harmony. Darwin’s answer 
would at first glance seem to assume differences in the eggs laid by a single 
queen capable of determining the difference in the individuals developed 
from these eggs; so that no special treatment (feeding) of an individual 
would be necessary to produce the ultimate differences in the matured indi¬ 
viduals. But the congenital differences may be potential and not definitive; 
the feeding treatment, namely, the addition of certain extrinsic or environ¬ 
mental factors, might be necessary to discover or make actual the latent or 
potential differences congenitally resident in the eggs. 
Still a third question arises in connection with the specialized conditions 
obtaining in modern ant communities. It is this: How have the compound 
and mixed communities, in which two ant species live in some kind or degree 
of symbiosis, arisen ? How has it come about that two species of ants which 
normally are deadly enemies ready to do battle with each other at any meet¬ 
ing—a condition which seems to be curiously general throughout the group 
of ants, not only different species being always ready to attack one another, 
but members of different communities of the same species showing a deadly 
animosity for each other—how is it that these two species have come to 
live peaceably together in a mixed community? 
In the first place in some of the cases the animosity still exists; the “thief” 
ants which live in other ants’ nests escape with their lives only because of 
their minute size and obscure coloring, their careful avoidance of detection, 
and the care with which they keep the galleries of their own part of the nest 
too small for the entrance of the hosts; they appear to manage this double 
household arrangement by vigilance, cleverness, and deceit. Cases of true 
symbiosis with mutual benefit are readily explicable by the selection theory. 
Their beginning is a little hard to understand, but an association with recip- 
