422 MORRIS M. WELLS 



his investigations into the biology of our North American ter- 

 mites and has added many facts of interest to our knowledge 

 of these insects. He has found that white ants occasionally 

 injure living trees and shrubs, in the southern part of the United 

 States. In Florida, they have at times done considerable dam- 

 age to the newly planted groves of orange trees by eating away 

 the bark and gradually girdling the tree. Similar damage has 

 been reported for apple, peach, pear, cherry, plum, apricot 

 and lemon. In California, pecan, chestnut and walnut are 

 attacked as well. In other parts of the United States a great 

 variety of shade trees are attacked. Snyder says, that all such 

 damage is more likely to occur in new soil or recently cleared 

 woodland, especially in the latter, if the stumps are still standing. 

 In the south, termites also occasionally injure the stems and 

 roots of a great variety of healthy field crops, both grain and 

 truck; they attack corn, cotton, sugar cane, rice, grasses, pota- 

 toes, and garden vegetables. In the prairie regions of Texas 

 and Arizona there is a tube forming termite that lives in the 

 ground and feeds on the roots of the grass. This species is often 

 found under and in, dry cow dung. It has been known to 

 destroy the vegetation over large areas of grazing land. 



DISPERSAL OF ANTS 



The first colony of the Argentine ant reported for the United 

 States was found in New Orleans in 1891. At the present time 

 there are myriads of colonies covering 1000 square miles of 

 territory and extending from Houston, Texas, to Wilmington, 

 N. C, and from Nashville, Tenn., to the mouth of the Missis- 

 sippi River (1). Food scarcity hastens the spread of the species. 

 The normal advance under ordinary conditions is from 300-400 

 feet a year, but rapid dispersal over large areas may take place 

 at times of heavy floods, as the ants will ride in floating rub- 

 bish of all sorts. They do not drown easily and when the rising 

 water floods their nests they frequently cluster together to form 

 a compact ball. The immature stages form the center of the 

 ball with the queens and the workers on the outside. As the 

 ball enlarges by the addition of other workers struggling alone 

 in the water, it slowly revolves and thus the mass is aerated. 

 This aeration is automatic and continuous, for the ants on the 

 under side of the ball are constantly striving to get out of the 



