CONTROL OF ARGENTINE ANT IN CALIFORNIA. 21 



hydrate crystals, previously dissolved in a small quanti^t^ 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 alnaost 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 ^'^ 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 [)oison under California conditions. 

 This led to experimenting wi'th various other formulas containing 

 arsenic as the basic poison and the ultimate deveUipment of a formula 

 thoroughly satisfactory inidcr California conditions. 



JO Barber, Ernest R. the argentine ant: DiaTRiBUTioN and control in the uNrrED states. 



U. S. Dept. Apr.. Bill. 377. 2:? p., r, ftp. 1910. 



