CONTROL OF ARGENTINE ANT IN CALIFORNIA. 21 
hydrate crystals, previously dissolved in a small quantity of water, and about one- 
half pound of strained honey. 
On July 22, 1918, an orchard experiment was started in which 
2-ounce spice tins about one-third filled with chloral-hydrate sirup 
according to the foregoing formula were hung on 48 trees attended 
by heavy trails of ants. The ants fed on this sirup greedily when 
first distributed and continued feeding freely throughout the dura- 
tion of the experiment, which was five months. The sirup started 
crystallizing about one month after being distributed and within 
six weeks most of the containers were partly filled with large crystals 
resembling rock candy. Although the sirup proved attractive, it 
did not appear to reduce the numbers of ants more rapidly than 
they bred, for ants were almost as numerous at the completion of 
the experiment as at the beginning. The tendency of this sirup to 
crystallize and its only partial action against ants show it to be not 
fully satisfactory as a poison. 
Arsenical Poisons. 
Arsenic in large quantities acts as a repellent to ants and its 
earliest use against the Argentine species was based on this action. 
Woodworth, experimenting later with this insect in the San Fran- 
cisco Bay region of California, obtained success in control by the 
use of an unboiled sweetened poisoned sirup containing about one- 
fourth of 1 per cent of sodium arsenite. 
In 1916 E. R. Barber 10 published the results of his efforts against 
the ant in Louisiana with an improved arsenical sirup and showed 
for the first time that eradication was possible over extensive areas. 
This system immediately appealed to the senior writer as offering a 
more practical solution of the ant problem in California than banding, 
which he had previously been using, and accordingly an experiment 
in controlling the ants about the laboratory was started in October, 
1916, and met with marked success. In December, 1916, an 
orchardist, who had observed the effectiveness of the system installed 
on the laboratory grounds, attempted control on his property by 
this method. This was the first control attempted in southern 
California in a citrus orchard. Others were thereupon induced to 
adopt the methods which Mr. Barber had proved eminently suc- 
cessful in Louisiana, and at the same time the writers started an 
investigation of the use of this poison under California conditions. 
This led to experimenting with various other formulas containing 
arsenic as the basic poison and the ultimate development of a formula 
thoroughly satisfactory under California conditions. 
io Barber, Ernest R. the argentine ant: distribution and control in the united states. 
U. S. Dept. Agr., Bui. 377. 23 p., 5 fig. 1916. 
