METHODS OF REPRESSION. 77 



respect even begins to compare with the losses suffered by the florists, 

 bee keepers, and orange growers. Early in the course of our studies 

 we undertook experiments looking to the development of measures 

 by which householders could obtain some reUef from this pest. 



A successful campaign against the Argentine ant is by no means 

 devoid of work, but the control measures thus far devised are no 

 more cumbersome or expensive than those employed in the warfare 

 against many other insects, and their intelligent employment is found 

 well worth the while in reduced annoyance from tliis pest. 



Studies of the ant's life history early developed the fact that per- 

 manent relief can be obtained only by actual destruction of the ants 

 themselves. The use of repellents only serves to permit the contin- 

 ued increase of the pests and to postpone the tune when more laborious 

 methods of warfare must be adopted. Not only is it necessary to 

 kiU the ants outright, but it is also necessary to adopt means which 

 will kill the queens. It is hardly necessary to call attention to the 

 difference between killing ants and the usual insects with which we 

 have to contend. If one kills a female gipsy moth or boU weevil, for 

 example, possible future progeny of that particular individual is made 

 impossible. Such is not the case when one destroys a worker ant, 

 for the rate of increase and the development of future generations are 

 in no wa}^ interfered with. This is true for the reason that the workers 

 take no part in reproduction, aU eggs being deposited by the queens. 

 That the destruction of foraging workers does not materially affect 

 the domestic economy of the colony or retard the rate of increase by 

 reducing the available food supply is shown by repeated observations 

 upon the nmnber of foragers required to keep the colony supphed with 

 food. In the artificial formicaries counts were made of the number 

 of workers going out for food during periods varying from five hours 

 to several days, and in no case did the number of foraging workers 

 out at one time exceed more than 1 per cent of the number of indi- 

 viduals in the colony. From this we naturally conclude that less than 

 1 per cent of the workers can keep the remainder, including the queens 

 and immature stages, supplied with food. These observations were 

 made in cases where the food supply was only a few inches from the 

 nest and was always in abundance. In times of food scarcity, and 

 when it is necessary for the workers to travel considerable distances in 

 order to reach a food supply, a larger percentage would have to engage 

 in foraging. Observations by the junior author upon a large number 

 of field colonies leads him to the conclusion that even under the most 

 adverse conditions not more than 10 per cent of the workers are 

 required for foraging. Under normal outdoor conditions the food 

 supply is abundant and at such times it is very doubtful whether more 

 than 2 per cent of the workers are ever engaged in foraging at any one 

 time. The futility of destroying the foraging workers is therefore 



