458 ANNUAL EEPOKT SMITHSONIAN INSTITUTION, 1912. 



the center of the instinctive activities to a much less degree than with 

 the bees. The greater individual autonomy of the ant workers, in 

 comparison with those of the bees, rests perhaps in large measure on 

 their greater longevity, which in the Formica species is generally 3 

 years. The duration of life of the queens may even exceed 12 years. 

 Polymorphism forms, it is true, the organic basis of the ant 

 societies, establishing division of labor between the members of the 

 same colony. But the evolution of the organic-psychic potentialities 

 slumbering within the egg results through the nursing instincts on 

 the part of the workers. What is intended to be a male or a female 

 appears, similarly as with the bees, to be already determined in ad- 

 vance within the egg.'^ But upon the differentiation of the various 

 forms of the female sex nursing has a determining influence. From 

 the fertilized eggs of one and the same Formica queen there may be 

 reared either wmged females or wingless workers or intermediate 

 forms. Particularly those mixed forms designated as pseudogynes, 

 which we shall find to be an effect of the Lomechusa-breeding, offer 

 proof of this explanation. 



2. SOCIAL PARASITISM AND SLAVERY AMONG THE ANTS. 



If the population of an ants' nest belongs to a single species of 

 ant it is called a simple (unmixed) colony. If, however, it is com- 

 posed of different species of ants, we speak, according to Forel's 

 example, either of compound nests or of mixed colonies ; in the former 

 the ants only live side by side; in the latter they combine into a 

 single household with common care of the young. These are the two 

 subdivisions into which the social symbiosis between ants of different 

 species divides. We shall here only give our attention to the mixed 

 colonies, and moreover with particular regard to the development of 

 social parasitism and of slavery. This is one of the most interesting 

 chapters in the phylogenetic development of instincts in the animal 

 kingdom. 



Peter Huber had already discovered that in the colonies of the 

 sanguine ants {Formica sanguinea) and of the AJmazon ants {Polyergus 

 rufescens) there live in addition to the master species the workers of 

 a slave species, which are robbed as pupae by the former from the 

 nests of the slave species and are then reared as auxiHary ants. 

 These are, therefore, slavemaking (dulotic) colonies. But there are 

 still other mixed colonies in which the auxiliary ants do not get into 

 association with the master species through captm'e; these range 

 among the social parasites. Since Charles Darwin (1859) diverse 

 hypotheses on the origin of slavery have been proposed. Recently, 

 by employing the phenomena of social parasitism for comparison, 



» That not only males but also workers originate from parthogenetic eggs (Reichenbach, Comstock, etc., 

 in Lasius, Tanner in Atta), is in any case a rare exception. 



