NESTS.—Ants differ greatly from the other Social Hymenoptera in the nature of their habitations. The social bees construct cells of wax crowded together in large numbers, and the wasps do the like with paper; the eggs and young being placed, each one in a separate cell, the combinations of which form a comb. Ants have, however, a totally different system; no comb is constructed, and the larvae are not placed in cells, but are kept in masses and are moved about from place to place as the necessities of temperature, air, humidity and other requirements prompt. The habitations of ants are in all cases irregular chambers, of which there is often a multiplicity connected by galleries, and they sometimes form a large system extending over a considerable area. Thus the habitations of ants are more like those of the Termites than those of their own allies among the Hymenoptera. They are chiefly remarkable for their great variety, and for the skilful manner in which they are adapted by their little artificers to particular conditions. The most usual form in Europe, is a {137}number of subterranean chambers, often under the shelter of a stone, and connected by galleries. It is of course very difficult to trace exactly the details of such a work, because when excavations are made for the purposes of examination, the construction becomes destroyed; it is known, however, that some of these systems extend to a considerable depth in the earth, it is said to as much as nine feet, and it is thought the object of this is to have access to sufficiently moist earth, for ants are most sensitive to variations in the amount of moisture; a quite dry atmosphere is in the case of many species very speedily fatal. This system of underground labyrinths is sometimes accompanied by above-ground buildings consisting of earth more or less firmly cemented together by the ants; this sort of dwelling is most frequently adopted when the soil in which the nests are placed is sandy; it is probable that the earth is in such cases fastened together by means of a cement produced by the salivary glands of the ants, but this has not been determined with certainty; vaulted galleries or tunnels of this kind are constructed by many species of ants in order to enable them to approach desired objects. [Illustration: Fig. 58—Portion of combined nest of _Formica fusca_ and _Solenopsis fugax_. (After Forel.) × ⅔. _f_, _f′_, Chambers of _Formica_, recognisable by the coarser shading; _s_, _s′_, chambers of the _Solenopsis_ (with finer shading); _s″_, opening in one of the chambers, the entrance to one of the galleries that connects the chambers of the Solenopsis; _w_, walls forming the foundations of the nest and the limits of the chambers.]