THE ARGENTINE ANT IN RELATION TO CITRUS GROVES. 61 



hand on the table, in addition to the poison, in order to approximate 

 field conditions as nearly as possible. With this apparatus and 

 method of feeding, ant colonies have been kept in a state of health 

 for nearly two years. In some cases, where the ants are confined for 

 prolonged periods without flesh food, they feed upon their own eggs 

 and young. 



Summary of Restxlts of Poisoning Tests. 



In conducting tests on nonimprisoned ants, difficulty was experi- 

 enced in determining the effect of the poison upon the ant colony. 

 Desertion of the nest may mean that the ants have been destroyed, 

 that the poison has merely impelled them to move, that they have 

 moved from need of better quarters, or that they have discovered 

 more abundant and suitable food elsewhere. The colony may move 

 slowly from the immediate neighborhood of the poison, but its scouts 

 continue to hang about the latter indefinitely. It may remain where 

 it is and follow the original trail near the poison without visiting it. 

 Slow migration may occur, giving the impression that the colony 

 is being destroyed, when such is not the case. From 26 to 298 days 

 were required to bring out the results. If the poison dosage is too 

 strong, the ants will leave it before much harm befalls them; if so 

 weak as to assure continuous feeding, its action is extremely slow. 

 The amounts of poisoned sirup consumed by the ants in field teste 

 varied from as low as 0.04 ounce per day over a period of 189 days 

 to as high as 1.2 ounces per day for 296 days. Dead worker ants 

 were found in or near the poison jars only in the case of three of the 

 poisons, viz, strychnine, potassium cyanid, and arsenic. Large 

 numbers of dead ants occurred often only at the jars containing 

 potassium cyanid. 



The poisons selected for a final testing upon imprisoned colonies 

 were strychnine, potassium cyanid, arsenic trioxid, lead arsenate, 

 mercuric and mercurous chlorid, tartar emetic, sodium arsenite, 

 chloral hydrate, and belladonna. The first symptoms of poisoning 

 shown by the imprisoned colonies are a strong desire on the part of 

 the workers for water and assiduous cleansing of the body, par- 

 ticularly the jaws. An ant will commonly regurgitate a dose of 

 poison, and a sister worker will cleanse her distended jaws with 

 great thoroughness, repeatedly going over them with the mandibles 

 and tongue. The next effect upon the colony is generally the death 

 of some of the young, followed by a slackening, and finally a cessa- 

 tion of oviposition. The young then die rapidly, followed by work- 

 ers, until all of both phases are dead. The queens then begin to do 

 their own foraging, and finally succumb to the poison, at times not 

 until several days after the demise of the last worker. 



