REPORT OF THE SOCIETY 53 



In enunciating my thesis I said that the ants are far more injurious than 

 useful. Are they useful, and to what extent? To what extent are they injurious? 

 Clear answers to those two questions must be given. 



I — Usefulness of Ants. 



Observation enables us to point out three cases especially, in which the ants 

 may be of service to the plants. 



1 . The ants while running over the plants, and searching for the honey-like 

 excretions on the aphids", worry them and knock them about. The more nu- 

 merous they are, the more violent is their action. Sometimes the aphids withdraw 

 their probosces from the plants; sometimes they even move on in search of a quiet- 

 er spot; moreover while moving along the edge of a leaf or beneath a branch, they 

 are thrown to the ground by ants in too great a hurry to avoid them. The fall 

 occasionally brings about their death, for they may be devoured by their enemies, 

 or trodden upon, or drowned in a pool of water. Even if no untoward accident 

 happen to the aphids, time is required for the changes that take place, and the 

 plant benefits. I admit that there is nothing very extraordinary in all that, but 

 after all one must give even ants their due. When we take into consideration the 

 fecundity of the aphids we must admit that if the ants destroyed some of the first 

 generation in the spring, the service rendered to the plant would be appreciable. 



2. The ants keep the aphids captive in the dwellings they have themselves 

 constructed. These stables in which milk cows, to use the expression of Lin- 

 naeus, are fed have long been known. I have often seen ants snatch aphids from 

 their favourite plant, and drag them into their underground nests. To judge by 

 their resistance the captives did not look upon the change as favourable; they 

 clung to every object along the way. Further, some of those aphids die before 

 attacking the roots. However difficult the explanation may be, the fact itself is 

 indisputable. Now it is at once evident that this is to the plant's advantage. I 

 am not at present discussing the general question, whether this habit of imprison- 

 ing and protecting the aphids in order to derive some benefit from them be 

 more useful to the aphids than to the plant. I am simply pointing out the fact 

 that the aphids during their captivity not infrequently meet with a premature 

 death, and the plant enjoys at least a momentary relief. This ought to cause no 

 surprise, the ant consults its own interests first and foremost, and however mar- 

 vellous we may consider the instinct which guides it, still from time to time in 

 particular circumstances it may be at fault. Its fallibility increases with the need 

 it has of the aphis. All the instances in which the ant helps the aphids, carries 

 them from one plant to another, and shelters them from the inclemencies of the 



