The Leaf-cutting Ants ((Ecodomd) are noted pests of central and tropical America; and, as is implied by their name, commit fearful havoc among trees, laboriously and persistently carrying off in their mouths, piece by piece, the foliage of trees and shrubs. The orange, lemon, and mango trees in particular have suffered from their attacks. Carbolic acid has been tried with success as a remedy against these ants, the use of this antiseptic killing large numbers; and corrosive sublimate in powder, sprinkled across their paths, has a deadly effect upon the leaf-cutters. Coal tar has also been employed against them. Gigantic black ants, averaging an inch in length, arc found in Central America. They are notable as being solitary in their habits, and possess well-developed eyes and formidable stings. These forms contrast with the gregarious and social ants, in which the eyes are com paratively weak, or may be rudimentary.
Certain curious little ants (Pseudomyrma bicolor) inhabit the hollow thorns of the " bull's horn " acacia of Central America. The horn-like thorns form the nest, the aperture being situated near the tip of the thorn. These ants pre serve the plant from the attack of the Leaf-cutting Ants, and also from mammals feeding upon it. The ants obtain a supply of food from the plant, in the shape of a honeylike secretion, found in a gland situated at the base of the leaflets. Protected by, and at the same time protecting the plant, the intimate relations between the acacia and the ants may be argued to possess a deeper significance than relates to a merely casual or chance connection. The Cecropia, or trumpet tree of Central America, is ten anted by ants, which obtain a sweet fluid, through the agency of brown scale-insects (Coccidce), kept by them in the cells of the trunk. This recalls the case of the aphides, or ordinary plant lice, the ants sucking the fluid from the scale-insects through a dorsal or back-pore. The queen-ant in her royal cell is attended by a special bevy of Ooccidce, who supply her with the requisite food. The Coccidce in America take the place of the European aphides as ant-cows, but the tropical ants appear to attach themselves to other insects also. Thus, the leaf-hoppers (Hembracis) are attended by ants, for the sake of the honey which the larvae exude. Those insects which are attended by ants are protected from the attacks of other animal forms; and the shelter given to the ants thus serves to protect the tree or shrub, and to save it from becoming exterminated.
The " soldier ants," referred to in the foregoing account of the Foraging Ants, are not peculiar to that race, many other species also possessing " soldiers." These forms, as has been already stated, appear to be merely neuters which have the jaws very largely developed, for the protection of the true neuters or workers, and for the defence of the nest generally. This further subdivision of the ant-community would seem to indicate an additional approach to the social arrangements which characterise the human state.
The reproduction and development of the ordinary ants may be very briefly touched upon in the present notice. The impregnation of the females in their aerial nuptial flight has been already alluded to, as also has the death of the males after the congress. The impregnated females are conveyed to the nest, and the deposition of eggs is pro ceeded with, the young forms being tended through their larvae and pupae stages by the assiduous neuters. Unlike the bees, several female ants may inhabit the same nest; and the swarming or exodus of the young ants, so far from having for its one and essential object the formation of a new colony, appears to be simply devoted to further reproductive measures. Thus, those that leave the nest are the fresh males and females, the sexual history of which has already been traced; and the nest thus remains a more or less permanent institution, changing its inmates only in part, and in exceptional circumstances alone giving origin to a new and independent colony.
The stings with which the neuters and females are armed constitute formidable organs of defence. The poison, to which the violent or painful effects of the sting are due, appears to consist of a definite chemical organic compound, the chief acid of which is known by the appropriate name of formic acid, the formula for this compound being CH 2 O 2 . Formic acid is also found in the glands attached to the pointed hairs of stinging-nettles. This acid, in itself possessing irritant qualities of a high order, also appears capable of producing even more serious effects when manipulated by chemical means.
Fig. 3.—Ant-lion (Myrmeleo formicaleo).
