REPORT OF THE SOCIETY 57 



some of the underground galleries beneath the plant aphids were kept. In digging 

 these galleries the ants, either accidentally or perhaps in order to allow the pris- 

 oners sustenance, had uncovered the roots and rootlets of the plant. In some 

 cases two-thirds of the roots were thus isloated, and therefore were unable to draw 

 the necessary nourishment from the soil. 



(b) The growth of some young Acer Negundo was very slow although they 

 were planted in good soil. With the exception of some ants that visited them 

 occasionally, they were not infested by insects. These ants, however, seemed to 

 have their nests near the roots. Through curiosity I gently uncovered the roots 

 of some saplings, and great was my surprise when I found them covered with small 

 white aphids. Innumerable ants mounted guard over these lodgers. Here again, 

 either to facilitate travelling or to help the aphids, the ants had laid bare the roots. 

 Thus was explained the slow growth of the maples. The only channels of nour- 

 ishment left to them were a few roots still embedded in the earth, and the small 

 quantity of sap thus obtained was taken by the aphids. 



(c) The flowers of the Amaranthus caudatus mentioned above droop and 

 trail on the ground. When the aphids swarm over them, the ants pile up the earth 

 around them and bury them. Thus they are cut off from the light and liable to rot. 

 The same will happen to any plant infested by aphids and visited by a number of 

 ants, if the stalk or a branch be bent to the ground. 



The reasons why the injury is greater in the case of smaller plants are: 



1. The stalk being shorter, the trips from the ground to the branches are 

 more frequent; and hence since the ants spend more time off the plant, there is 

 greater need of underground galleries. 



2. The smaller roots are more easily isolated, whereas large roots would be 

 laid bare only on one side. 



This will be sufficient, I think, to prove that we must not look upon the ants 

 as useful because of their relations with the aphids; for we have seen that their 

 misdeeds outweigh incomparably the good they accomplish. Therefore they must 

 be prevented from settling near plants which are attacked by aphids, especially if 

 the plants be annuals or biennials. The aphids themselves will certainly not com- 

 plain for there is nothing to prove that they set a high value on the friendship of 

 the ants; on the contrary the desperate efforts they make to escape from captivity 

 show that a benefit would be conferred upon them by this measure. 



[N.B. — This paper was originally written in French. For the translation I am 

 indebted to Rev. F. Downes, S.J.] 



