Returning to Corumbá on the evening of December 21, we were joined by the other members of the expedition and immediately proceeded on the up-river voyage toward São Luis de Caceres. A short side-trip was made up the Rio São Lourenço, with brief stops at various points where there were evidences of game, but very little was added to the collections. On January 1, early in the morning, we halted at a place where there were fresh jaguar tracks on the river-bank. Colonels Roosevelt and Rondon, and Kermit, accompanied by a number of _camaradas_ and the dogs, immediately took up the trail and disappeared among the trees. We spent a part of the day on board the steamer, and the remainder collecting in the immediate vicinity. One of the men ran into a nest of maribundi wasps; one of the enraged insects stung him on the head and for several hours the poor fellow was in great agony. His head was swollen to an enormous size, and his companions bathed it constantly with water to relieve the pain; they feared he would die. I have very good reasons for remembering these wasps. While on the Chaparé River, in Bolivia, one of them crawled under the mosquito-net covering my cot; when I retired at night I put my arm on the insect and was stung four times before it could be captured. The effect of the poison was as rapid as it was remarkable. It produced a kind of paralysis within about five minutes, which the prompt action alone of my companion prevented from ending fatally; but more extraordinary still, the same symptoms returned regularly at six months’ intervals during the following two years. Each attack lasted from a week to ten days. The day gradually drew to a close, and finally darkness settled over the landscape, but there was no sign of the hunting-party. The captain, therefore, began to cruise up and down the river, giving frequent blasts of the ship’s whistle, for it was feared that the hunters might have become lost. After an hour or so we suddenly rounded a sharp bend and heard a loud voice singing cheerfully somewhere on the bank. A boat was sent in the direction whence the sound came, and after a short time it returned with Colonels Roosevelt and Rondon. They had been pursuing the jaguar through forest and swamp for twelve hours on foot, and without food or drink. Their clothing was torn and covered with mud; it had been necessary to swim frequently, in their clothes, holding their rifles above their heads; the lagoons were infested with _piranhas_ and crocodiles. In running through the vegetation fire-ants and wasps had been swept from the leaves and branches, and the insects had been quick to retaliate with bites and stings. But Colonel Roosevelt had enjoyed the experience thoroughly and at once sat down to a hearty dinner, during the course of which we heard the story of the hunt. Kermit returned some hours later. Most of the _camaradas_ were so tired they spent the night in the forest and did not come in until late the next morning.