FORMICA, in natural history, the at or emmet, a genus of insects of the order Hymenoptera. Feelers four, unequal, with cylindrical articulations, placed at the tip of the lip, which is cylindrical and nearly membranaceous ; antennae filiform; a small erect scale between the thorax and abdomen ; females and neuters arm ed with a concealed sting; males and fe males with wings, but to neuters there are no wings. This is a gregarious and very industrious family, consisting, as the generic character shows, of males, fe males, and neutrals. The last are well known insects, who construct the nests or ant-hills, who labour with unremitting assiduity for the support of themselves and the males and females, and who guard with such ferocity the larvx, or what are usually denominated ant's eggs. They wander about all day in search of food or materials for the nest, and assist each other in bringing home what is too heavy or large for such as have attempted it. They bring out of their nest, to expose to the warmth of the sun, the newly hatch ed larvx, and feed them till they are able to provide for themselves. In the even ing they consume together whatever has been collected during the day, and do not, as is commonly supposed, lay up any store for the winter. They are very co veteous of aphides, and are at the same time very careful not to injure them, feeding only on their honey-like excre ment. In the conduct of the ant towards the aphis, a remarkable degree of intelli gence is displayed. 'When the aphis does not readily give out this fluid, the ant applies its mandibles to its abdomen, and by a gentle pressure indicates its wants. Sometimes this tender creature is carried borne by the ant in considerable numbers, and treated with the most marked attention; in return it supplies that industrious insect with a con siderable quantity of food, and bears the same relation to it as that useful animal, the cow,does to man. This is exemplified
in a yellowish ant not uncommon in Penn sylvania. (See Antis.) The ant is ea gerly sought after by the formica-leo, and various birds. Ants feed on animal and vegetable substances, devouring the smaller kinds of insects, caterpillars, &c. as well as fruits of different kinds. The largest of the European ants is the F. her culanea, or great wood ant, of a chesnut colour, which is found in dry woods of fir, where it inhabits a large nest or hil lock, composed of dry vegetable frag ments, chiefly of fir-leaves: the nest is internally distributed into several paths or tubes, converged towards a central part, and opening externally ; in the cen tre reside the larvx, which are nursed by neutral ants. When full grown, they en velop themselves in oval white silken cases, in which they undergo their change into the chrysalis state, and at length emerge in their complete form. About seventy species have been described.
F. nigra is the common black ant of Europe. The great desire that ants have for animal food has been made use of by anatomists, who when they wish to ob tain the skeleton of an animal too small or delicate to admit of being prepared in the usual way, dispose the animals in a proper position in a small box, with per forations in the lid, and deposit it in a large ant-hill, in consequence of which, after a certain time, the whole of the soft er parts are eaten away by these insects, and the skeleton remains in its proper position.
F. rufa contains an acid which has un dergone a chemical analysis, &c. See FORMIC acid.