560 Saw-flies, Gall-flies, Ichneumons, 



vorum) not only in the same genus but among closely allied forms. This 

 fact also suggests that the instincts of the same species may be so generalized 

 as to enable it to /unction like man, either as a slave or master, according to 

 the circumstances." 



And this leads us to consider briefly that extremest form of consociation 

 between two ant species, namely, the so-called dulosis, the living together of 

 slave-makers and slaves. To put summarily the result of various careful 

 studies of dulotic communities made by both European and American 

 observers, it may be said that this condition has grown out of the general 

 instinct that most ants show, to obtain when and where possible the larvae 

 and pupae of other ant species for food. From a raid on a neighboring com- 

 munity and the immediate devouring of as many larvae and pupae as possible 

 to a similar attack and feast plus the bringing home of a supply of this choice 

 food to be stored for eating through the next few days is a natural, and as 

 exemplified by numerous observed cases, an actual step. Then if the booty 

 be large in amount, it is inevitable that some of the pupae shall transform 

 in the new nest. Now, are these newly issued workers to be at once 

 attacked and eaten? This depends on whether the proper stimulus is 

 present or not. As practically certainly determined by numerous observa- 

 tions and experiments the stimulus for attack and war among ants (as 

 well as bees) is odor; recognition of nest mate and perception of intruder 

 or foreigner depends probably solely on the sense of smell, and the 

 stimulation of this sense has come during the evolution of the instincts 

 of ants to be a stimulus to direct reflexive action; the odor of the home 

 community determines friendly behavior, the odor of any other community 

 gives direct rise to attack. Now, this odor has several component ele- 

 ments; one, for example, inherited (by the inheritance of a characteristic 

 metabolism) from the queen, so that descendants of a common mother, or 

 of sister-mothers (common grand-maternal inheritance), have an odor with 

 something in common; another element and a strong one is, however, the 

 nest odor compounded of all the individual odors in a community and gradu- 

 ally taken on by each hatching young. If the young be removed from one 

 community and be hatched in another they seem to take on the odor 

 of the second community. And so the living booty brought back by the 

 raiders, issuing in the new nest, becomes endowed with the odor of the new 

 community and is unmolested. But the instinct of the hatched workers 

 is to work; and so work they do. If their work is of advantage to the raider 

 community, natural selection will do the rest. In the beginning there 

 were no slave-makers; raiders there were which raided other nests, not for 

 slaves, but for food. But bringing home extra supplies of this food, which 

 hatched and lived and worked in the new nest, evolution from food to slaves 

 and from raiders to slave-holders has naturally taken place. Now such 



