THE HABITS OF ANTS IN GENERAL. 177 



populous, lead a nomadic existence, since they must continually seek 

 fresh hunting grounds in order to obtain the requisite amount of food. 

 The ants of the three remaining subfamilies, though often predatory, 

 have adapted themselves to a more varied diet and many of them have 

 come to rely almost exclusively on vegetable food. The following 

 are the sources from which these insects as a family derive their 

 nourishment : 



1. The original food of ants consists of other insects, especially 

 helpless larvae and other terrestrial arthropods such as spiders, myrio- 

 pods and isopods, the dying imagines of the countless insects which 

 fall to the earth when their life-work is completed, those which are 

 just leaving their pupa-cases, and the fragments rejected by insec- 

 tivorous birds and mammals. 



2. The larvae and pupa? of ants are a favorite food of certain 

 species of Eciton and Formica, which are sufficiently intrepid to pillage 

 the nests of other species. And, in fact, in times of need many 

 species will eat their own offspring, which may, therefore, be con- 

 sidered as an ever-present and available food-supply stored up against 

 periods of famine. 



3. The excretions of plants, such as the sweet liquids exuding from 

 the leaves and especially from the floral and extrafloral nectaries, the 

 sap escaping from wounded stems, etc. 



4. The honey-dew excreted by plant-lice (aphids), mealy bugs 

 (coccids) and leaf-hoppers (membracids), and the secretions of the 

 caterpillars of the butterfly family Lycaenidae. These liquids are, of 

 course, plant juices that have undergone certain changes in the ali- 

 mentary tract or glands of the insects. 



5. The seeds of plants, especially of grasses and berries, drupes 

 and fruits of all kinds, that have been injured by birds or other insects 

 or by falling to the ground, for the ants are unable to gnaw through 

 the tense skins or rinds of fruits. Some hypogaeic species also feed 

 on bulbs or tubers, the tender bark of roots, or the cotyledons of 

 germinating seeds. 



6. One tribe of ants, the Attii of tropical America, lives exclusively 

 on fungus hyphae, which they cultivate on vegetable substances carried 

 into the nests. 



Probably no single species of ant is able to draw on all of these 

 sources of nutrition, but many species are sufficiently adaptable to util- 

 ize several of them. The fungus-growing ants are the most highly 

 specialized in their diet and next to these some of the seed-storing, 

 or harvesting species. Many ants, however, are more or less omni- 

 vorous, and many find it an easy matter to pass from one kind of food 



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