METHODS OF KEPKESSION. 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 within their living chambers, the cadavers always 
being removed expeditiously and often to a considerable distance. 
This makes it extremely difficult to tell, by examination of a colony 
in nature, how many of the individuals have been killed by 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 did 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 distance from it, food not poisoned was also kept at all 
times. The workers from tins colony therefore had their choice 
between poisoned and nonpoisoned food. A few workers died each 
day, the larva? all succumbing a few days after inauguration of the 
experiment. At the end of about 20 days the colony seemed demor- 
alized and discouraged, the queen ceased to lay, and the workers did 
not work with their accustomed activity. At the end of 44 days all 
individuals were dead, the queen having lived until near the end of 
the period. 
Many solutions and mixtures containing white arsenic (arsenic 
trioxid) were tested in various ways and the one which gave by far 
the best results was made by combining one-fourth gram of arsenic 
trioxid with 20 grams of granulated sugar in 100 cc. of water. 1 When 
placed in a small dish anywhere within the foraging range of a colony 
this preparation would be greedily taken for a few hours, after which 
the ants would not touch it as long as it remained in the same position. 
When 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 this 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. 
