538 Saw-flies, Gall-flies, Ichneumons, 



surface, built up as a mound or hillside, of more or less symmetry and greater 

 or less size. This part above ground may be composed chiefly or wholly 

 of soil brought up from below surface, or may be partly or wholly made 

 up of bits of wood, grass and weed stems, chaff or pine-needles. The 

 nest may be made under a stone or log, or be placed in a wholly exposed 

 place. Most ants keep their nests fairly near the surface, but a few are 

 deeply subterranean miners. Still other species tunnel out their corridors 

 and rooms in wood an old log or stump, dry branches, or what not while 

 yet others live in the stems of plants, in old plant-galls, in hollow thorns and 

 spines; finally, a few make nests of delicate paper or tie leaves together with 

 silken threads. Very wonderful are some of the interrelations between 

 certain plants and certain ant species in tropic regions, whereby the plant 

 seems to have developed suitable cavities for the accommodation of the 

 ants, whose presence is in turn advantageous to the plant by the protection 

 it affords against the ravages of certain leaf-eating insects which are repelled, 

 or rather attacked as prey, by the ants. In many cases two ant species will 

 live together in a compound or mixed nest, the relation between the two 

 species being (a) simply that of two close neighbors, friendly or unfriendly; 

 (b) that of two species having their nests with "inosculating galleries" and 

 their "households strangely intermingled but not actually blended"; (c) 

 that of one species, usually with workers of minute size, which lives in or 

 near the nests of other species and preys on the larva; or pupae or surrepti- 

 tiously consumes certain substances in the nests of their hosts some different 

 larger species that is, the relation of thief and householder; (d) that of two 

 species living in one nest but with independent households, one of these 

 species living as a guest or inquiline at the expense of the food-stores of the 

 other, but consorting freely with their hosts and living with them on terms 

 of mutual toleration or even friendship; and (e) that of slave-maker and 

 slave, a relation not at all rare and readily observed all over our country. In 

 addition certain other as yet little studied cases of the living together of dis- 

 tinct ant species occur which, when understood, may reveal yet other sym- 

 biotic relations. 



Inside the nest the eggs are laid by the queen or queens in large numbers, 

 not in separate cells as with the wasps and bees, but in little piles heaped 

 together in various rooms and sometimes moved about by the workers. 

 The hatching larvae, tiny, white, footless, helpless, soft-bodied grubs, are 

 fed by the workers either a predigested food regurgitated from the mouth, 

 or chewed fresh insects, caught and killed by the workers, or dry seeds or 

 other vegetable matter brought into the hive and stored in the "granary" 

 rooms. A single species of ant may use all these different kinds of food, 

 but for the most part the ants belonging to one species habitually do not. 

 The primitive food consists of seeds and cut-up insects. The importance 



