We always passed the nights ashore; the temperature in our cabin aboard the _Nyoac_ was 118° F., so we much preferred to sling our hammocks among the trees, where it was cooler. One morning upon awakening I was surprised to see the gently waving palm-leaves overhead. It seemed queer that I should have forgotten to adjust the mosquito net the night before; but an investigation showed that the greater part of the netting had been carried away during the night by the _carregador_ ants. In my several experiences with these insects I have never known them to carry away woollen clothing, but all articles of cotton to which they had access were destroyed. The jabiru storks were nesting on the São Lourenço; we saw several of their great platform nests of sticks perched in the crotches of giant trees. The young storks, two in number and fully feathered, were continually exercising their limbs by running back and forth in the nest, flapping their wings all the while, preparatory to launching forth into the big world. If we tossed short sticks up to them they caught them in their bills, held on for a few moments, then dropped them. Caimans were particularly plentiful on the upper Paraguay. Scores of the evil-looking reptiles lay on the sand-banks, with wide-open mouths and staring, glassy eyes. A fringe of trees flanked the water; through them we could see the boundless wastes of _pantanales_ beyond. Troops of black howler monkeys ambled leisurely away as the boat drew near; the males only were black, the females being of a straw-color. There were immense flocks of a species of gray-throated, green parrakeets; some of them were building enormous nests of sticks in the branches. When a single tree contained three or four of the huge structures, its strength was strained to the breaking-point, for some of the nests were five or six feet across and contained hundreds of pounds of material; but not all of them were of this size; some were composed of no more than an armful of sticks and were occupied by a single pair of birds. The larger ones harbor dozens of birds. The nesting cavities had been in the under-side of the structures; entrance to them was gained through tubular openings underneath.