172 HOUSEHOLD INSECTS 



over the surface. Their action in this respect is similar 

 to that of earthworms, the value of which was revealed 

 to us by the classic investigations of Darwin. Ants are 

 also important agents in aiding in the decomposition of 

 organic substances. Their work in this respect is little 

 appreciated or realized because it is invisible. It must 

 be remembered, however, that this work of ants is gradual, 

 incessant, and extends through tremendously long periods 

 of time. 



Again, ants are great insect destroyers. Their food 

 consists, in great part, of the juices and tissues of dead 

 insects or of insects that they kill. The interesting driver 

 ants of the Old World and the legionary ants of tropical 

 Africa pass through a territory killing and devouring 

 multitudes of living insects, rats and mice. Hunter 

 and Hinds tell us that there are 12 species of ants known 

 to attack the immature stages of the Mexican cotton boll 

 weevil. "In some cases more than half of the immature 

 stages in fields have been found to be destroyed by ants 

 alone. To find 25 per cent so destroyed is not a rare 

 occurrence." 



On the other hand, certain household species of ants 

 are very annoying and troublesome. Moreover, the leaf- 

 cutting ants of tropical America are very injurious to 

 plants. They will strip a fruit tree of its foliage in a very 

 short time. One species of these leaf-cutting forms 

 (Atta texana) found in Texas attacks cotton, corn, fruit- 

 trees, sorghum, and other plants, and has become of con- 

 siderable economic importance. In some places land is 

 not planted on account of fear of attack by these ants. 



The mound-building prairie ant (Pogonomyrmex occi- 

 dentalis), distributed over a large part of the western 



