THE ARGENTINE ANT : BISTBIBUTION AND CONTEOL. 3 



Texarkana, Ark.. Nashville, Tenn., Memphis, Tenn., Augusta, Ga., 

 Atlanta, Ga., Charleston, S. G., and Wilmington, N. C. 



DISPERSION. 



Under natural conditions the Argentine ant spreads very slov^ly , and 

 this spread is controlled to a large degree by the available food supply. 

 Like most other species of ants, the Argentine ant is a very indus- 

 trious forager, and a shortage of food tends to hasten its dispersion. 

 In October, 1914, a small infestation covering the most of two city 

 blocks was found in Memphis, Tenn. The ant numbers could not 

 have increased to any appreciable extent during the rather long 

 and cold winter of 1914-15, and yet in the early part of the following 

 June the infestation was found to involve nearly the whole of five 

 blocks. In October, 1915, it developed that the boundaries had not 

 been extended, though the ant numbers had greatly increased. The 

 food supply must have increased as fast as did the numbers of ants. 



In several instances frequent observations made at points on the 

 frontier of the infestation developed the fact that the normal ad- 

 vance will average from 300 to 400 feet a year. The abundance of 

 native ants has some influence on this advance, since the Argentine 

 ant will not tolerate any of the native species, and in consequence a 

 continuous fight is waged all along the frontier. 



Heavy, flooding rains are undoubtedly a factor in the natur^,! dis- 

 tribution of this ant, and in the vast region drained by the Mississippi 

 Eiver and its tributaries it will be remembered that there are at least 

 two dangerous flood seasons and sometimes more, which contribute to 

 and accelerate the distribution of this species. Lumber, rotting trees, 

 uprooted shrubs, cane growth, fruit, vegetables, and all manner of 

 refuse contribute to the mass of matter borne on the crest of flood 

 water, and in this the ants seek refuge and are involuntarily trans- 

 ported. Nature has endowed this species with a remarkable habit of 

 self-preservation from drowning in times of floods, for when rising 

 water floods their nests and no other means of escape are presented 

 they cluster together and form a compact ball. The immature stages 

 form the center of this ball, with the queens and workers as the outer 

 portion. As the ball enlarges from the addition of other workers 

 which had been struggling alone in the water it gradually revolves. 

 It is kept revolving slowly by the outside workers continually striv- 

 ing to reach the top of the ball, thus permitting air to reach the 

 interior. The writer has had only one opportunity of witnessing the 

 formation of a ball of this kind. After a 5-inch rainfall several 

 balls, none more than 2 inches in diameter, were observed. According 

 to reliable authorities, such balls have been observed on many oc- 

 casions, some of them from 6 to 8 inches in diameter. The ants in 



