(B) Familiar Ants (Formica) (cont.)
Food of Ants
The food of ants has formed a debatable point ever since the attention of naturalists was directed to the investigation of their economy. As already remarked, many species are truly carnivorous, and prey upon the soft parts of other insects, and particularly of larvae, which they are enabled to seize and capture with little danger and trouble.
The well-known partiality of ants for animal food is taken advantage of by those who wish to obtain the hard parts or skeletons of animal forms; since by placing an animal body within reach of an ant-colony, the soft parts are gradually eaten away, and the harder portions are left intact. In tropical climates, rats, mice, and poultry, even in a living state, are said to succumb to the attack of these creatures; and man himself, as related by Prévost in his Histoire Général des Voyages, is even subject to the attacks of ants. Prévost relates that an Italian missionary in Congo was awakened from sleep by his Negroes, with the intelligence that an immense horde of ants was invading his house. Before he could rise they had already covered his legs, and the floor of his house was carpeted by a thick layer of the invading forms. Fire seemed to be the only preventive to their onward march; and it was stated that cows were known to be devoured in their stalls by these creatures.
These remarks may be viewed as applying more particularly to the white ants or termites, of which an account will be given afterwards.
For sugar ants seem to have a special predilection; and they appear not only to obtain the saccharine matter from vegetables, but also to abstract it from animal sources. The aphides, or plant lice, become in this way the subjects of very extraordinary attentions on the part of ants. The plant lice possess a glandular structure, situated at the extremity of the abdomen, which communicates with the external surface by two small ducts. This gland secretes a sweet or saccharine liquid of viscous nature, of which ants are extremely fond, and the aphides appear to be literally "milked" by their smaller neighbours. The antennae of the ants in this case also appear to be the media of intercourse between the aphides and themselves, and by touching the abdomen of the plant lice with the antennae, a drop of the saccharine liquid exudes from the gland, which is eagerly seized upon by the ants; and in this fashion the milking process is continued until the ant is satisfied.
The aphides, in this instance, appear voluntarily to surrender themselves for the purpose of affording the saccharine matter; but it has been also alleged that certain species of ants keep aphides within their nests for the purpose of affording the desired matter. Whether or not this alleged domestication of the aphides by ants is to be deemed worthy of belief yet remains to be proved. A single aphis may be occasionally seen surrounded by three or four ants, -- the latter ordinarily finding the aphides on the leaves of plants and in their natural habitat.
The association of ants and aphides, strange as it may seem, is not, however, without its parallels in the history of the ant-colony. Thus wood-lice are not infrequently found as apparently normal guests within the ant-nest; and Siva of Pisa observed a species of grasshopper, to which he has given the name Gryllus myrmecophilus, which inhabits the nest of an Italian ant. The ant-nest, in fact, appears to be the normal habitation of this grasshopper.
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