THE ARGENTINE ANT: DISTRIBUTION AND CONTROL. 17 



The experiment was duplicated, except that the sirups were placed 

 in waxed paper bags tacked on fig trees. These bags each held a 

 gill of sirup, and sponges were placed in the sirup to allow easy 

 access of the ants. At the time of conducting the experiment the 

 figs were ripening and the ants were visiting the trees in immense 

 numbers. It will be seen from the second part of Table I that the 

 results were substantially the same as in the indoor experiments. 

 The two experiments may be summarized as follows : 



The most concentrated sirup (2 ounces sodium arsenite) at- 

 tracted great numbers of ants in only 32 counts, few ants in 34 

 counts, and no ants whatever in 39 counts. 



The standard Nickels sirup (1 ounce sodium arsenite) attracted 

 great numbers in 62 counts, few ants in 25 counts, and no ants in 

 18 counts. 



The half-strength solution (| ounce sodium arsenite) attracted 

 great numbers in 88 counts, few ants in 12 counts, and no ants in 5 

 counts. 



The quarter-strength solution ( ounce sodium arsenite) attracted 

 great numbers in 92 counts, few ants in 4 counts, and no ants in 9 

 counts. 



The experiments prove, therefore, that the excessive quantities of 

 the arsenic in a sirup will cause it to become repellent. The observa- 

 tions also indicate that the sirup decomposed more rapidly as the 

 amount of the sodium arsenite increased. 



Dr. W. E. Cross, research chemist of the sugar experiment station 

 at Audubon Park, was consulted with regard to the various defects 

 in the Nickels sirup. His explanations and suggestions, which were 

 of great importance in the further conduct of the investigations, are 

 given below. 



When granulated sugar (or sucrose) is heated, it is partially 

 changed to invert sugar (or glucose), and if to this is added sodium 

 arsenite, which has an alkaline reaction, chemical decomposition 

 takes place. When heated this reaction is hastened and the com- 

 pound becomes darker and darker. On account of the instability of 

 the sirup, it will further decompose on standing and the final prod- 

 uct will be a substance with an unpleasant odor and taste. The 

 addition of a small quantity of tartaric acid to the sugar sirup 

 before adding the sodium arsenite will produce a greater inversion 

 of the sucrose, thus lessening the danger, of crystallization, and will 

 neutralize the alkalinity of the sodium arsenite, preventing decom- 

 position. If a slight acid reaction is obtained the sirup will keep 

 indefinitely. The inversion of the sucrose reduces the sweetness of 

 the sirup, and to balance this 7 per cent of pure hone} 7 is added. 



