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 relief 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 this 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 time when more laborious 
methods of warfare must be adopted. Not only is it necessary to 
kill 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 boll 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 way interfered with. This is true for the reason that the workers 
take no part in reproduction, all 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 number of foragers required to keep the colony supplied 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 
