THE HYMENOPTERA 371 



slaves. Sla,very is not Essential with all the kinds of ants where it is 

 known, colonies having no slaves being able to carry on their lives unaided 

 by slaves. With certain species, however, the situation is different. 

 In these the workers have mandibles so constructed that they are unable 

 to gather food, excavate their nests or care for the young. Accordingly 

 they make forays on the nests of other species, bringing back larvae and 

 pupae which on becoming adult are slaves which do the work of the colony 

 and care for their captors, both as adults and during their early stages. 



The honey ants, so-called, include those species in which the crop is 

 capable of great distention, and this power is made use of by collecting 

 honey-dew and storing it until the abdominal mass is enormously dis- 

 tended and (in some species) about the size of a large currant, such in- 

 dividuals becoming animated food reservoirs. These members of the 

 colony hang on the ceilings of their galleries, withdrawing from the 

 regular duties of the other workers. The reason for the existence of 

 such a peculiar habit is suggested by the fact that the honey ants are 

 confined to dry plains and desert regions, being found in North America, 

 South Africa and Australia. They are therefore probably true reservoirs 

 of nourishment which may be drawn upon during periods of drought, 

 when the ants must remain for some considerable time in their nests. 



Some ants raise fungi upon which to feed, about one hundred kinds 

 which do this being known. These insects in most cases go in large num- 

 bers to trees and some climb the trees and cut off the leaves while other 

 members of the colony pick these up from the ground where they have 

 fallen and carry them to their nests where the fungus is grown on them. 



A few species of ants are obnoxious to man, either by invading houses, 

 making their nests in lawns or in trees, or by to some extent protecting 

 injurious insects. 



The Argentine Ant (Iridomyrmex humilis Mayr.) is a native of 

 South America which probably reached this country between 1880 and 

 1890 at New Orleans and now is present nearly everywhere in most of the 

 southern tier of states, and in California as far north as San Francisco. 



The adults (Fig. 387) are brown in color. The queens are about a 

 quarter of an inch long, the males about half that length, and the workers 

 about a tenth of an inch long. Their summer nests "may be located 

 anywhere under sidewalks, under the sills of houses, in brick piles, stone 

 piles, under a piece of board or a piece of tin, in an old tin can in fact, 

 in any place convenient to the food supply. In the winter months there 

 is a tendency to concentrate into larger colonies, and they seek warm, 

 dry, secure nesting places in which to hibernate" (E. R. Barber). 



Egg production is probably quite large perhaps 50 or more per day 

 under favorable conditions and an average of 40 days in warm weather 

 is required for development from the laying of an egg to the emergence 

 of the adult worker. 



