In this country forays of a colony of For mica sanguinea upon a colony of a black species of Formica, for the purpose of making slaves of them, has been not infrequently observed. Slavery (duloris) is known to exist only be tween ants belonging to the same subfamily, the species of only four genera being known to practise slavery. In Europe the 'paragon of dulotic ants° is Polyergus rufescens, or the "amazon° ant, as the workers are very warlike, though they are in other respects helpless and completely dependent on their slaves, dying of starvation if deprived of them. Darwin's ex planation of the origin of the slave-making habits is that they were originally due to the predatory instincts of ants in general, seen in their carrying off the pupa: of other species, which, becoming stored as food, and finally developing would in their new abode do what work they could; and this habit of collecting pupae for food might be rendered permanent for the purpose of raising slaves.
Sound Produced by Ants.— Certain spe cies of ants are evidently not deaf, because capable of producing sounds which must be heard by others of their own kind. Thus Myr mica rubra has a sound-producing apparatus, a strigil, or file on the seventh abdominal seg ment (Janet); another ant of this group (Siena laviceps) is provided with a stridulating file: and in the ronerids there is a stridulating organ consisting of a band of very fine raised lines on the second segment behind the node. Other ants (Polyrhachss) tap on the surface of a leaf with their heads, producing a sound audible to human ears, as does an Assamese species by scraping the end of its abdomen on the dry leaves of its nest.
Senses of Ants.— While ants may be blind and deaf, none are known to be destitute of the sense of smell. The olefactory organs are little sensory pits in the antennae. It is un doubtedly by means of their sense of smell that ants recognize the members of their own nest, and those of other species which they treat as enemies. It is probably by this means
that they distinguish their friends from their enemies. Thus the cause may be the result of reflex action, rather than any special degree or kind of intelligence.
Parasitic Ants with No Workers.— Such are the ants of the genera Anergates and Epcecus• in the former the male and females are helpless, incapable of leaving the nest and dependent on the attentions of the workers of another genus (Tetramorium) which live with them. This strange relationship seems thus far inexplicable.
Symbiosis in Ants.—The relation between ants and plants is very intimate, and it assumes different phases. See SYMBIOSIS.
Commensalism.— Ants' nests are so many apartment or boarding hives. A vast number of beetles, aphides, cockroaches, flies and arach nids take up their abode in the nests of ants, where they are allowed by their willing or un willing hosts to feed on the excretions of the ants themselves or their food. The fostering instincts of ants thus seem to be extended in various degrees to their guests and thus lay the foundation for this semi-parasitic community. Upward of 1,500 species of Arthropoda are known to live in more or less cordial relations with their hosts.
Bibliography.— Huber, (Recherches sur les Moeurs des Fourmis Indigenes' (Paris and Geneva 1810) ; Ford, (Les Fourmis de la Suisse> (Geneva 1874) ; Lubbock, 'Ants, Bees, and Wasps' (New York 1894) ; McCook, 'The Natural History of the Agricultural Ant of Texas' (Philadelphia 1879); (The Honey Ants of the Garden of the Gods,' etc. (Philadelphia 1882); Emery, 'Beitrage zur Kenntniss der Nordamerikanischen Ameisenfauna) Jahrbuch,) Vols. VII and VIII (1893-94) ; Wheeler, The Compound and Mixed Nests of American Ants,' 'American Naturalist,' Vol. XXXV (Boston 1901) ; Wheeler (Ants: Their Structure, Development and (New York 1910).