366 THE FOXTISTDING OF COLOISTIES BY ATTA SEXDENS. 



nant factor in this gradual retrogression is mainly the overabundance 

 of workers, the activities of which perpetually hamper the queen. 

 It is partly due also to the rapid development of the fungus garden 

 which precludes the possibility of its care and inspection being accom- 

 plished by the mother ant. Apparently, also, the new mode of 

 fungus culture is uncongenial to the queen, and as a consequence she 

 gives up her own share in this work. The care of the metamorphosed 

 pupse is, as we have already seen, the first responsibilit}^ that the queen 

 relinquishes into the hands of the workers. In the matter of tending 

 the larvae during the transitional period, the duty is narrowed down 

 to simply supplying them with eggs, and this, as already noted, is 

 more and more delegated to the workers. In consequence of this 

 steady enlargement of the fungus garden the larvjfi (and the eggs as 

 well) are gradually removed from the domain of the mother ant. It 

 is not surprising that at first the larvae continue to be fed with eggs, 

 since at this period the quantity of kohlrabi is small, being barely 

 sufficient for the adult workers. Nevertheless, I once noticed a small 

 worker offering a half-eaten kohlrabi to a larva, and finally mashing 

 it up in a very practical way in front of its mouth. In this way a 

 beginning is doubtless made in the further feeding of the larvae with 

 kohlrabi, which comes to be a general thing as soon as the necessary 

 supply is obtainable. The time at Avhich the feeding of the queen 

 w^ith kohlrabi begins is at present undertermined, a process seen by 

 Professor Goeldi and repeateclh' by me as well, in the case of old 

 colonies. In all probability the workers adopt this source of supply 

 as soon as kohlrabi is plentiful enough. If my theory regarding the 

 feeding of the queen by the workers during the transitional period 

 proves to be the correct one, this period would then be the natural 

 time of changing from the original egg diet to a vegetable diet upon 

 kohlrabi. 



Although it becomes evident from what has been previousl}^ here 

 recorded, that in the case of Atta sexdens the foundation of a new 

 colony is possible by means of an isolated fertile female and often 

 doubtless takes place in nature, this does not in any sense exclude the 

 possibility of such a colony being founded by adoption. A number 

 of my investigations bearing on this point have been fully successful. 

 For example, fig. 26 represents a colony resulting by adoption of a 

 queen on the part of workers from an old nest. The fertile female, 

 held in captivity for a month, and taken during the breeding period, 

 was carried away by the workers to a subterranean nest. At first 

 she sought to share in the care of the fungus garden and the young 

 brood, but was prevented from doing so to any considerable extent by 

 the swarm of workers, and at length seemed more and more to sink 



