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wet and the mosquitoes, it was one of the most uncomfortable nights I have ever passed.
The waning moon was sufficiently high at four o'clock to allow us to bring the long dreary night to an end, and to commence paddling up the river again. As the day broke the rain ceased, the mists cleared away, our spirits revived, and we forgot our discomforts of the night in admiration of the beauties of the river. The banks were hidden by a curtain of creeping and twining plants, many of which bore beautiful flowers, and the green was further varied here and there by the white stems of the cecropia trees. Now and then we passed more open spots, affording glimpses into the forest, where grew, in the dark shade, slender-stemmed palms and beautiful tree-ferns, contrasting with the great leaves of the Heliconiæ. At seven we breakfasted on a sand-bank, and got our clothes and blankets dried. There were numerous tracks of alligators, but it was too early to look for their eggs in the sand; a month later, in March, when the river falls, they are found in abundance, and eaten by the canoe-men. At noon we reached the point where the Seripiqui, a river coming down from the interior of Costa Rica, joins the San Juan about thirty miles above Greytown. The Seripiqui is navigable by canoes for about twenty miles from this point, and then commences a rough mountain mule-track to San José, the capital of Costa Rica. We paddled on all the afternoon with little change in the river. At eight we anchored for the night, and although it rained heavily again, I was better prepared for it, and, coiling myself up under an umbrella beneath the tarpaulin, managed to sleep a little.
We started again before daylight, and at ten stopped at a small clearing for breakfast. I strolled back a little way into the gloomy forest, but it was not easy to get along on account of the undergrowth and numerous climbing plants that bound it together. I saw one of the large olive-green and brown mot-mots (Momotus martii), sitting upon a branch of a tree, moving its
long curious tail from side to side, until it was nearly at right angles to its body. I afterwards saw other species in the forests and savannahs of Chontales. They all have several characters in common, linked together in a series of gradations. One of these features is a spot of black feathers on the breast. In some species this is edged with blue, in others, as in
the one mentioned above, these black feathers form only a small black spot nearly hidden amongst the rust-coloured feathers of the breast. Characters such as these, very conspicuous in some species, shading off in others through various gradations to insignificance, if not extinction, are known by naturalists to occur in numerous genera ; and so far they have only been explained on the supposition of the descent of the different species from a common progenitor.
As I returned to the boat, I crossed a column of the army or foraging ants, many of them dragging along the legs and mangled bodies of insects that they had captured in their foray. I afterwards often encountered these ants in the forests, and it may be convenient to place together all the facts I learnt respecting them.
ECITONS, OR FORAGING ANTS.— The Ecitons, or foraging ants, are very numerous throughout Central America. Whilst the leaf-cutting ants are entirely vegetable feeders, the foraging ants are hunters, and live solely on insects or other prey; and it is a curious analogy that, like the hunting races of mankind, they have to change their hunting-grounds when one is exhausted, and move on to another. In Nicaragua they are generally called “ Army Ants.” One of the smaller species (Eciton predator) used occasionally to visit our house, swarm over the floors and walls, searching every cranny, and driving out the cockroaches and spiders, many of which were caught, pulled, or bitten to pieces and carried off. The individuals of this species are of various sizes; the smallest measuring one and a quarter lines, and the largest three lines, or a quarter of an inch.
I saw many large armies of this, or a closely allied species, in the forest. My attention was generally first called to them by the twittering of some small birds, belonging to several different species, that follow the ants in the woods. On approaching to ascertain the cause of this disturbance, a dense body of the ants, three or four yards wide, and so numerous as to blacken the ground, would be seen moving rapidly in one direction, examining every cranny, and underneath every fallen leaf. On the flanks, and in advance of the main body, smaller columns would be pushed out. These smaller columns would generally first flush the cockroaches, grasshoppers, and spiders. The pursued insects would rapidly make off, but many, in their confusion and terror, would bound right into the midst of the main body of ants. A grasshopper, finding itself in the midst of its enemies, would give vigorous leaps, with perhaps two or three of the ants clinging to its legs. Then it would stop a moment to rest, and that moment would be fatal, for the tiny foes would swarm over the prey, and after a few more ineffectual struggles it would succumb to its fate, and soon be bitten to pieces and carried off to the rear. The greatest catch of the ants was, however, when they got amongst some fallen brushwood. The cockroaches, spiders, and other insects, instead of running right away, would ascend the fallen branches and remain there, whilst the host of ants were occupying all the ground below. By-and-by up would come some of the ants, following every branch, and driving before them their prey to the ends of the small twigs, when nothing remained for them but to leap, and they would alight in the very throng of their foes, with
the result of being certainly caught and pulled to pieces. Many of the spiders would escape by hanging suspended by a thread of silk from the branches, safe from the foes that swarmed both above and below.
I noticed that spiders were generally most intelligent in escaping, and did not, like the cockroaches and other insects, take shelter in the first hiding-place they found, only to be driven out again, or perhaps caught by the advancing army of ants. I have often seen large spiders making off many yards in advance, and apparently determined to put a good distance between themselves and their foe. I once saw one of the false spiders, or harvest-men (Phalangido), standing in the midst of an army of ants, and with the greatest circumspection and coolness lifting, one after the other, its long legs, which supported its body above their reach. Sometimes as many as five out of its eight legs would be lifted at once, and whenever an ant approached one of those on which it stood, there was always a clear space within reach to put down another, so as to be able to hold up the threatened one out of danger.
I was much more surprised with the behaviour of a green, leaf-like locust. This insect stood immovably amongst a host of ants, many of which ran over its legs, without ever discovering there was food within their reach. So fixed was its instinctive knowledge that its safety depended on its immovability, that it allowed me to pick it up and replace it amongst the ants without making a single effort to escape. This species closely resembles a green leaf, and the other senses, which in the Ecitons appear to be more acute than that of sight, must have been completely deceived.