METHODS OF REPRESSION. 85 



had been entirely submerged at times during hard rains. No dead 

 ants were found in the empty nest; any such, if present, were taken 

 away at or before the time of vacating the formicary. The ants will 

 not tolerate dead wdthin their hving chambers, the cadavers always 

 being removed expechtiously and often to a considerable distance. 

 This makes it extremely difficult to tell, by examination of a colony 

 in nature, how many of the intU\aduals have been killed b}^ any poison 

 fed to the workers. The action of the colony in moving outside the 

 zone of danger was observed in many subsequent experiments in 

 which poisoned food was used, and this gave us the clue to the use of 

 sweetened arsenical mixtures as repellents for driving the colonies 

 away from infested situations. The same phenomenon, improperly 

 understood, has been responsible for the conclusion, arrived at by 

 several experimenters, that the use of such mixtures was actually 

 exterminating the ants, their absence after use of the poison being 

 ascribed to their death and not to their migration to a safer place. 



That the mixtures containing lead arsenate, such as those just 

 described, do destroy the individuals within the nest and that their 

 continued consumption by the ants would result in extermination if 

 the colony cUd not move away from them, were established by experi- 

 ments made with colonies kept in artificial formicaries where migra- 

 tion from the poison was made impossible. In one such experiment 

 a small amount of the mixture last described (1 part lead arsenate 

 paste, 1 part pulverized sugar, and 2 parts honey) was kept constantly 

 on the food table of a colony in the formicarium. On the same table, 

 but a short cUstance from it, food not poisoned was also kept at all 

 times. The workers from tliis colony therefore had their choice 

 between poisoned and nonpoisoned food. A few workers died each 

 day, the larvae all succumbing a few days after inauguration of the 

 experiment. At the end of about 20 days the colony seemed demor- 

 afized and cUscouraged, the queen ceased to lay, and the workers did 

 not work wdth their accustomed activity. At the end of 44 days all 

 incUviduals were dead, the queen having lived until near the end of 

 the period. 



Many solutions and mixtures containing wliite arsenic (arsenic 

 trioxid) were tested in various ways and the one wliich gave by far 

 tlie best results was made by combining one-fourth gram of arsenic 

 trioxid mth 20 grams of granidated sugar in 100 cc. of water.* Wlien 

 placed in a small dish anywhere witliin the foraging range of a colony 

 tliis preparation would be greedily taken for a few hours, after wMcli 

 the ants would not touch it as long as it remained in the same position. 

 ^Mien the dish was moved a few feet away or placed in another part 



1 To give warning of its dangerous nature it is well to add to thLs mixture sufficient confectioner's color 

 paste to dye it a brilliant red or green. Fruit juices, as of raspberry or similar fruits, may be added to 

 accomplish the same end. 



