The Naturalist on the River Amazons [221]
of nearly equal size throughout. The task occupies about four days: when finished, the enclosed caterpillar becomes sluggish, its skin shrivels and cracks, and there then remains a motionless chrysalis of narrow shape, leaning against the sides of its silken cage.
Many other kinds are found at Ega belonging to the same cocoon- weaving family, some of which differ from the rest in their caterpillars possessing the art of fabricating cases with fragments of wood or leaves, in which they live secure from all enemies while they are feeding and growing. I saw many species of these; some of them knitted together, with fine silken threads, small bits of stick, and so made tubes similar to those of caddice-worms; others (Saccophora) chose leaves for the same purpose, forming with them an elongated bag open at both ends, and having the inside lined with a thick web. The tubes of full- grown caterpillars of Saccophora are two inches in length, and it is at this stage of growth that I have generally seen them. They feed on the leaves of Melastoniae, and as in crawling, the weight of so large a dwelling would be greater than the contained caterpillar could sustain, the insect attaches the case by one or more threads to the leaves or twigs near which it is feeding.
Foraging Ants--Many confused statements have been published in books of travel, and copied in Natural History works, regarding these ants, which appear to have been confounded with the Sauba, a sketch of whose habits has been given in the first chapter of this work. The Sauba is a vegetable feeder, and does not attack other animals; the accounts that have been published regarding carnivorous ants which hunt in vast armies, exciting terror wherever they go, apply only to the Ecitons, or foraging ants, a totally different group of this tribe of insects. The Ecitons are called Tauoca by the Indians, who are always on the look-out for their armies when they traverse the forest, so as to avoid being attacked. I met with ten distinct species of them, nearly all of which have a different system of marching; eight were new to science when I sent them to England. Some are found commonly in every part of the country, and one is peculiar to the open campos of Santarem; but, as nearly all the species are found together at Ega, where the forest swarmed with their armies, I have left an account of the habits of the whole genus for this part of my narrative. The Ecitons resemble, in their habits, the Driver ants of Tropical Africa; but they have no close relationship with them in structure, and indeed belong to quite another sub-group of the ant-tribe.
Like many other ants, the communities of Ecitons are composed, besides males and females, of two classes of workers, a large- headed (worker-major) and a small-headed (worker-minor) class. the large-heads have, in some species, greatly lengthened jaws, the small-heads have jaws always of the ordinary shape; but the two classes are not sharply-defined in structure and function, except in two of the species. There is in all of them a little difference among the workers regarding the size of the head; but in some species this is not sufficient to cause a separation into classes, with division of labour; in others, the jaws are so monstrously lengthened in the worker-majors, that they are incapacitated from taking part in the labours which the worker- minors perform; and again, in others the difference is so great that the distinction of classes becomes complete, one acting the part of soldiers, and the other that of workers. The peculiar feature in the habits of the Eciton genus is their hunting for prey in regular bodies, or armies. It is this which chiefly distinguishes them from the genus of common red stinging-ants, several species of which inhabit England, whose habit is to search for food in the usual irregular manner. All the Ecitons hunt in large organised bodies; but almost every species has its own special manner of hunting.
Eciton rapax.--One of the foragers, Eciton rapax, the giant of its genus, whose worker-majors are
Many other kinds are found at Ega belonging to the same cocoon- weaving family, some of which differ from the rest in their caterpillars possessing the art of fabricating cases with fragments of wood or leaves, in which they live secure from all enemies while they are feeding and growing. I saw many species of these; some of them knitted together, with fine silken threads, small bits of stick, and so made tubes similar to those of caddice-worms; others (Saccophora) chose leaves for the same purpose, forming with them an elongated bag open at both ends, and having the inside lined with a thick web. The tubes of full- grown caterpillars of Saccophora are two inches in length, and it is at this stage of growth that I have generally seen them. They feed on the leaves of Melastoniae, and as in crawling, the weight of so large a dwelling would be greater than the contained caterpillar could sustain, the insect attaches the case by one or more threads to the leaves or twigs near which it is feeding.
Foraging Ants--Many confused statements have been published in books of travel, and copied in Natural History works, regarding these ants, which appear to have been confounded with the Sauba, a sketch of whose habits has been given in the first chapter of this work. The Sauba is a vegetable feeder, and does not attack other animals; the accounts that have been published regarding carnivorous ants which hunt in vast armies, exciting terror wherever they go, apply only to the Ecitons, or foraging ants, a totally different group of this tribe of insects. The Ecitons are called Tauoca by the Indians, who are always on the look-out for their armies when they traverse the forest, so as to avoid being attacked. I met with ten distinct species of them, nearly all of which have a different system of marching; eight were new to science when I sent them to England. Some are found commonly in every part of the country, and one is peculiar to the open campos of Santarem; but, as nearly all the species are found together at Ega, where the forest swarmed with their armies, I have left an account of the habits of the whole genus for this part of my narrative. The Ecitons resemble, in their habits, the Driver ants of Tropical Africa; but they have no close relationship with them in structure, and indeed belong to quite another sub-group of the ant-tribe.
Like many other ants, the communities of Ecitons are composed, besides males and females, of two classes of workers, a large- headed (worker-major) and a small-headed (worker-minor) class. the large-heads have, in some species, greatly lengthened jaws, the small-heads have jaws always of the ordinary shape; but the two classes are not sharply-defined in structure and function, except in two of the species. There is in all of them a little difference among the workers regarding the size of the head; but in some species this is not sufficient to cause a separation into classes, with division of labour; in others, the jaws are so monstrously lengthened in the worker-majors, that they are incapacitated from taking part in the labours which the worker- minors perform; and again, in others the difference is so great that the distinction of classes becomes complete, one acting the part of soldiers, and the other that of workers. The peculiar feature in the habits of the Eciton genus is their hunting for prey in regular bodies, or armies. It is this which chiefly distinguishes them from the genus of common red stinging-ants, several species of which inhabit England, whose habit is to search for food in the usual irregular manner. All the Ecitons hunt in large organised bodies; but almost every species has its own special manner of hunting.
Eciton rapax.--One of the foragers, Eciton rapax, the giant of its genus, whose worker-majors are