362 THE STUDY OF INSECTS 



where certain workers take them and chew them into fine bits which are 

 then used as a medium on which to grow fungi as food for the members 

 of the colony. 



One common species, Atta texdna, occurs in central Texas. It is 

 known as the parasol ant because files of the individuals may be seen, 

 each with a piece of leaf held over its back like a tiny parasol, which it 

 is carrying to its nest. This ant is often destructive to cotton, corn, 

 fruit-trees and other plants for where it is abundant it will soon strip a 

 plant of its leaves. 



Most of the fungus-growing ants are confined to tropical and sub- 

 tropical America but one species is found as far north as New Jersey. 



THE ARGENTINE ANT AND ITS ALLIES 



In this subfamily the pedicel of the abdomen consists of a single 

 segment and there is no constriction between the first and second seg- 

 ments of the gaster. These ants often possess in addition to the poison 

 glands, anal glands which excrete a foul smelling, sticky fluid, which is 

 used as a means of defense in their combats with other ants. 



Only about a dozen species have been described from our fauna and 

 most of these are southern. Certain tropical species build carton nests 

 attached to trees and some of our species make carton nests under stones. 

 The members of this subfamily are especially fond of honey-dew and 

 attend aphids and coccids to secure it. The most important species of 

 the subfamily in our fauna is the following. 



The Argentine ant, Iridomyrmex humilis. ■ — This is an introduced 

 species, which has become an exceedingly serious pest in the Gulf States 

 and in Southern California. Its injuries are of two kinds: first, as a 

 household pest, entering and overrunning dwellings; and second, as an 

 orchard pest. Its injuries in orchards are due to the fact that it protects 

 aphids and coccids in order to secure the honey-dew that they excrete. 

 The ants drive away the insect enemies of the aphids and coccids, which 

 gives the latter a chance to multiply to an abnormal extent. 



THE TYPICAL ANTS 



The typical ants form a large subfamily containing many of our field 

 ants and also those very interesting slave-making ants and the honey- 

 ants. The pedicel of the abdomen 

 consists of a single segment (Fig. 605). 

 In this respect the typical ants are like 

 the preceding subfamily. 



The following are some of our more 

 common species. 



The carpenter ant, Camponotus Jier- 

 _ t . , culcamis pennsyhanicus. — This is one 



Fie. 60s. — A typical ant. - ,, , ' -- , T , 



of the largest of our common ants. It 

 is the large black species that builds its nests in the timbers of build- 

 ings, in logs and in the trunks of trees. Frequently it builds in the 

 dead interior of a living tree, excavating a complicated series of chambers. 

 The mound-building ant, Formica exsectoides. — This .species is the 

 builder of our largest ant-hills; these are often three feet in height and 



