The Saüba ant is peculiar to tropical America, and, though it is injurious to the wild native trees of the country, it seems to have a preference to the coffee and orange trees and other imported plants. The leaves which the Saüba cuts and carries away are used to "thatch the domes which cover the entrances to their subterranean dwellings, thereby protecting from the deluging rains the young broods in the nests beneath." The insects proceed according to a most orderly method, "the heavily-laden workers, each carrying its segment of leaf vertically, the lower edge secured in its mandibles, troop up, and cast their burdens on the hillock; another body of laborers place the leaves in position, covering them with a layer of earthy granules, which are brought one by one from the soil beneath." The labors of this curious insect are immense, and no obstacles stop their excavations. An allied species of Rio de Janeiro worked a tunnel under the bed of the river Parabyba, at a place where it is as broad as the Thames at London Bridge. These ants are sad rogues, being household plunderers and robbers of the farinha, or mandioca meal, of the poor inhabitants of Brazil; and Mr. Bates was obliged to lay trains of gunpowder along their line of march to blow them up, which in the end resulted in scaring the burglars away. We have already alluded to the massive heads possessed by the major and subterranean kinds of neuters, and stated that the work is done by the worker minor or small-headed kind. With regard to the function of the large-headed worker major, Mr. Bates was unable to satisfy himself:
"They are not the soldiers or defenders of the working portion of the community, like the armed class in the termites, or white ants, for they never fight. The species has no sting, and does not display active resistance when interfered with. I once imagined they exercised a sort of superintendence over the others; but this function is entirely unnecessary in a community where all work with a precision and regularity resembling the subordinate parts of a piece of machinery. I came to the conclusion, at last, that they have no very precisely defined function. They cannot, however, be entirely useless to the community, for the sustenance of an idle class of such bulky individuals would be too heavy a charge for the species to sustain. I think they serve in some sort as passive instruments of protection to the real workers. Their enormously large, hard, and indestructible heads may be of use in protecting them against the attacks of insectivorous animals. They would be, on this view, a kind of pièces de résistance serving as a foil against onslaughts made on the main body of workers."
But the third order, the subterranean kind, we are told, is the most curious of all:
"If the top of a small, fresh hillock, one in which the thatching process is going on, be taken off, a broad cylindrical shaft is disclosed, at a depth about two feet from the surface. If this be probed with a stick, which may be done to the extent of three or four feet without touching bottom, a small number of colossal fellows will slowly begin to make their way up the smooth sides of the mine. Their heads are of the same size as those of the other class (worker major); but the front is clothed with hairs instead of being polished, and they have in the middle of the forehead a twin ocellus, or simple eye, of quite different structure from the ordinary compound eyes on the side of the head. This frontal eye is totally wanting in the other workers, and is not known in any other kind of ant. The apparition of these strange creatures from [{188}] the cavernous depths of the mine reminded one, when I first observed them, of the Cyclopes of Homeric fable. They were not very pugnacious, as I feared they would be, and I had no difficulty in securing a few with my fingers. I never saw them under any circumstances than those here related, and what their special functions may be I cannot divine."
The naturalist traveller, in the midst of much that interests and delights him, has to put up with a great deal that is annoying, and Mr. Bates proved no exception to the rule. The first few nights when at Caripí, he was much troubled with bats; the room where he slept had not been occupied for several months, and the roof was open to the tiles and rafters:
"On one night," he says, "I was aroused about midnight by the rushing noise made by vast hosts of bats sweeping about the room. The air was alive with them; they had put out the lamp, and when I relighted it, the place appeared blackened with the impish multitudes that were whirling round and round. After I had lain about well with a stick for a few minutes they disappeared amongst the tiles, but when all was still again they returned, and once more extinguished the light. I took no further notice of them and went to sleep. The next night several got into my hammock; I seized them as they were crawling over me, and dashed them against the wall. The next morning I found a wound, evidently caused by a bat, on my hip."
Bats remind us of the vampire, a native of South America, concerning whose blood-sucking properties so much discussion has been from time to time raised. The vampire bat was very common at Ega; it is the largest of the South American species. Of this bat Mr. Bates writes:
"Nothing in animal physiognomy can be more hideous than the countenance of this creature when viewed from the front; the large leathery ears standing out from the sides and top of the head, the erect, spear-shaped appendage on the tip of the nose, the grin, and glistening black eyes, all combining to make up a figure that reminds one of some mocking imp of fable. No wonder that imaginative people have inferred diabolical instincts on the part of so ugly an animal. The vampire, however, is the most harmless of all bats, and its inoffensive character is well known to residents on the banks of the Amazon."
That much fable has attached itself to the history of this curious creature we are perfectly convinced, and that its blood-sucking peculiarities have been grossly exaggerated we must allow. When this bat has been said to perform the operation of drawing blood "by inserting its aculeated tongue [Footnote 26] into the vein of a sleeping person with so much dexterity as not to be felt, at the same time fanning the air with its large wings, and thus producing a sensation so delightfully cool that the sleep is rendered still more profound," it is clear that the mythical element exists to a great extent in the narrative; but our author's assertion that "the vampire is the most harmless of all bats" does not tally with the statements of other naturalists of considerable note. Mr. Wallace says he saw the effects of the vampire's operations on a young horse, and that the first morning after its arrival the poor animal presented a most pitiable appearance, large streams of clotted blood running down from several wounds on its back and sides:
[Footnote 26: An Expression used by Mr. Wood in his "Zoögraphy.' It is enough to remark that no known bat has an aculeated.]