"Presently on the right bank of the river, and thus to the left of the steamer's bow, appears that curious low-lying country of the Chaco, the alternate forests, swamps and pastures that extend from here northwards through the entire length of Paraguay and well into Bolivia on the other side. There are orchids hanging up aloft among the foliage now, and doubtless a monkey or two among the denser clumps of woodland. But these pioneer creatures of the Tropics to the north are rare enough here, and in any case are invisible. Their presence thus is generally unsuspected by the newcomer, which is not the case with the mosquitoes and those clouds of other _bichos_, whose numbers increase in the most amazing fashion with almost every hour that goes by. "Indeed, did one judge of the winged pests of these neighbourhoods by the myriads which abound above the fervid waters, the outlook would be sufficiently unpromising even to the most mosquito-hardened of men. The song of this plague is continuous of an evening now, and when the daylight has vanished in the abrupt fashion in which it is wont to fade away in these latitudes, the electric globes of the steamer are all but obscured by the insects that dance about them so thickly as to resemble dense clouds of smoke that roll in confused masses about a half-seen flame! Fortunately, these river reaches--most beloved of all the haunts of the winged creatures--do not afford a fair and moderate sample of the insect life of these latitudes, quite considerable enough though the usual run of this is wont to be. "Arrived at the Argentine town of Corrientes, one of the most important strategic spots in the whole river system has been reached. To one bound upstream this is the parting of the river ways. A few miles to the north of the town the choice is open to the traveller whether he will turn to the right and ascend the waters of the Alto Paraná, with Argentina on his right hand and Paraguay on his left, or whether he will keep straight on to the north and reverse this territorial situation, having Argentina on his left and Paraguay on his right.