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- 



