82 THE ARGENTINE ANT. 



A solution of potassium cyanid was made at tlie strength, of 

 1 ounce of 98 per cent cyanid to 1 gallon of water. The site selected 

 for the experiment was the area surrounding a few small cotton 

 plants which were heavily mfested with the cotton louse, Aphis 

 gossypii Glov. Around the plants the earth was literally honey- 

 combed by numerous small colonies of the Argentine ant, the workers 

 of which were in constant attendance upon the aphides. The 

 experiment was made at 11 a. m. on a bright day, with the tempera- 

 ture at about 77° F., when the workers were busily visiting the lice 

 and foragmg elsewhere for food and when the activities of the colonies 

 were at about a maximum. The solution was sprayed onto the 

 trails of traveling ants and the ground itself was sprayed until 

 thoroughly wet with the solution. By the time the spraying was 

 completed the odor of the cyanid was so strong as to affect the 

 operator. In spite of this the solution did not immediately kill the 

 workers with which it came in contact, but they appeared to suc- 

 cumb within about five mmutes after the spraying. Five hours 

 after the spraying the odor of cyanid was still very strong and the 

 number of dead workers on the surface of the ground fully equaled, 

 or exceeded, the number of living ones in sight at the time of spraying. 

 Many live workers were busily engaged in carrying away the dead. 

 The ground was examined and thousands of living ants m all stages — 

 workers, pupse, larvae, and eggs — were found less than half an inch 

 below the surface. Two days later the area w^as again examined 

 and the ant colonies were apparently as j^opulous as ever. This 

 and other experiments seemed to demonstrate the impracticability 

 of using this solution for destruction of the colonies, particularly as 

 the earth would have to be treated with a sufficient amount of the 

 solution to saturate it thoroughly to a depth of several inches. This 

 would probably destroy all vegetation, would be expensive, and 

 would involve the risk of injury to or loss of life by the operator and 

 others. For species constructmg compact nests havmg single or 

 few openings the solution is doubtless effective but, o^ving to the 

 multitudinous openings and galleries of the Argentine ant nest, 

 destruction could be accomplished only by the use of enormous 

 quantities of the solution. 



The resistance of this species to hydrocyanic-acid gas was well 

 illustrated m experiments made in attemptmg to fumigate the 

 winter trap-boxes in orange groves. These trap-boxes are described 

 more in detail on pages 95-96. They were about 2 feet wide, 2 feet 

 high, and 3 feet long, made of rough lumber and filled wdth decaying 

 cottonseed and hay. During the winter months these boxes con- 

 tained enormous colonies. For fumigating them to destroy these 

 colonies galvanized-iron covers were made (see Plate XII) which 

 would fit over them easily. A 6-inch hole was made in the top of each 



