531 AXTS. 



l : ormica fusca iu>l which they have found are brought up from 

 the depths of tin- galleries, appropriated and dragged home, often 

 a distance of fori\ meters or more. If the plundered nest still 

 contains pup;e, the rohher.s return on the same or following days and 

 carry off the remainder, but if there are no pupae left they do not 

 return. How do the l\>l\cryns know whether there are pupae remain- 

 ing? It can be demonstrated that smell could not attract them from 

 such a distance, and this is even less possible for sight or any other 

 sense. Memory alone, ;'. e., the recollection that many pupae still remain 

 behind in the plundered nest can induce them to return." The same 

 reasoning, of course, applies to the cases of simple foraging, and the 

 attendance of ants day after day on the same plant-lice. 



2. Recognition of Nest-mates and Aliens. Bethe has also endeav- 

 ored to show that the mutual recognition of ants is a mere chemoreflex, 

 without a trace of sensation or perception, but in this he has failed 

 even more signally than in his reflex interpretation of the homing 

 behavior. The existence of mixed colonies like those of the slave- 

 holders and other social parasites shows very clearly that ants, both 

 young and adult, not only learn to accept alien ants as friends, but 

 may actually treat as enemies members of their own colony from which 

 they were separated as pupae. These facts and their bearing on Bethe's 

 contention have been clearly analyzed by Wasmann as follows : " An 

 ant could be born only with the amicable reaction to the odoriferous 

 secretions of those ants with whom she is connected by descent. No 

 one would be willing to state that the amicable reaction towards any 

 kind of odor of an alien colony or alien species is innate, for this would 

 patently contradict the observed facts. Therefore we can regard as 

 innate only the amicable reaction of an ant towards the family odor of 

 her own species and her own colony, from which she is descended, but 

 not the amicable reaction to the odor of alien ant colonies and species, 

 which are in fact recognized as " enemies " by their different odors. 

 Xow the auxiliaries that are reared in the colonies of predatory ants 

 react amicably to the odor of the alien species (the so-called mistresses 

 in the colony), but are hostile to the odor of their own sisters, from 

 whose colony they were kidnapped as pupae. Therefore the amicable 

 reaction of ants to the odor of their own colony is not innate, but is 

 acquired individually by the single ants. This individual acquisition 

 occurs during the period in which the young, freshly developed worker 

 begins to harden and take on her adult coloration. During this period 

 her own definite individual odor first develops, and during this period 

 there develops in her antennae the olfactory sense, by means of which 

 she is able to distinguish the odor of her own nest-mates from those 



