第10章

The underground abodes of this wonderful ant are known to be very extensive.The Rev.Hamlet Clark has related that the Sauba of Rio de Janeiro, a species closely allied to ours, has excavated a tunnel under the bed of the river Parahyba, at a place where it is broad as the Thames at London Bridge.At the Magoary Rice Mills, near Para, these ants once pierced the embankment of a large reservoir; the great body of water which it contained escaped before the damage could be repaired.In the Botanic Gardens, at Para, an enterprising French gardener tried all he could think of to extirpate the Sauba.With this object, he made fires over some of the main entrances to their colonies, and blew the fumes of sulphur down the galleries by means of bellows.Isaw the smoke issue from a great number of outlets, one of which was seventy yards distant from the place where the bellows were used.This shows how extensively the underground galleries are ramified.

Besides injuring and destroying young trees by despoiling them of their foliage, the Sauba ant is troublesome to the inhabitants from its habit of plundering the stores of provisions in houses at night, for it is even more active by night than in the day-time.At first I was inclined to discredit the stories of their entering habitations and carrying off grain by grain the farinha or mandioca meal, the bread of the poorer classes of Brazil.At length, whilst residing at an Indian village on the Tapajos, Ihad ample proof of the fact.One night my servant woke me three or four hours before sunrise, by calling out that the rats were robbing the farinha baskets--the article at that time being scarce and dear.I got up, listened, and found the noise was very unlike that made by rats.So, I took the light and went into the storeroom, which was close to my sleeping-place.I there found a broad column of Sauba ants, consisting of thousands of individuals, as busy as possible, passing to and fro between the door and my precious baskets.Most of those passing outwards were laden each with a grain of farinha, which was, in some cases, larger and many times heavier than the bodies of the carriers.

Farinha consists of grains of similar size and appearance to the tapioca of our shops; both are products of the same root, tapioca being the pure starch, and farinha the starch mixed with woody fibre, the latter ingredient giving it a yellowish colour.It was amusing to see some of the dwarfs, the smallest members of their family, staggering along, completely hidden under their load.The baskets, which were on a high table, were entirely covered with ants, many hundreds of whom were employed in snipping the dry leaves which served as lining.This produced the rustling sound which had at first disturbed us.My servant told me that they would carry off the whole contents of the two baskets (about two bushels) in the course of the night, if they were not driven off;so we tried to exterminate them by killing them with our wooden clogs.It was impossible, however, to prevent fresh hosts coming in as fast as we killed their companions.They returned the next night; and I was then obliged to lay trains of gunpowder along their line, and blow them up.This, repeated many times, at last seemed to intimidate them, for we were free from their visits during the remainder of my residence at the place.What they did with the hard dry grains of mandioca I was never able to ascertain, and cannot even conjecture.The meal contains no gluten, and therefore would be useless as cement.It contains only a smallrelative portion of starch, and, when mixed with water, it separates and falls away like so much earthy matter.It may serve as food for the subterranean workers.But the young or larvae of ants are usually fed by juices secreted by the worker nurses.

Ants, it is scarcely necessary to observe, consist, in each species, of three sets of individuals, Or, as some express it, of three sexes--namely, males, females, and workers; the last-mentioned being undeveloped females.The perfect sexes are winged on their first attaining the adult state; they alone propagate their kind, flying away, previous to the act of reproduction, from the nest in which they have been reared.This winged state of the perfect males and females, and the habit of flying abroad before pairing, are very important points in the economy of ants;for they are thus enabled to intercross with members of distant colonies which swarm at the same time, and thereby increase the vigour of the race, a proceeding essential to the prosperity of any species.In many ants, especially those of tropical climates, the workers, again, are of two classes, whose structure and functions are widely different.In some species they are wonderfully unlike each other, and constitute two well-defined forms of workers.In others, there is a gradation of individuals between the two extremes.The curious differences in structure and habits between these two classes form an interesting, but very difficult, study.It is one of the great peculiarities of the Sauba ant to possess three classes of workers.My investigations regarding them were far from complete; I will relate, however, what I have observed on the subject.

When engaged in leaf-cutting, plundering farinha, and other operations, two classes of workers are always seen (Figs.1 and 2, page 10).They are not, it is true, very sharply defined in structure, for individuals of intermediate grades occur.All the work, however, is done by the individuals which have small heads (Fig.1), while those which have enormously large heads, the worker-majors (Fig.2), are observed to be simply walking about.