grasshoppers, of embracing a slender vertical stem with its four fine front legs, and moving cunningly round so as to keep the stem always in front of it to screen itself from sight. Only other grasshoppers are silent when alarmed, and the silence and masking action are related, and together prevent the insect from being detected. But this particular species, or race, or colony, living on the sides of the isolated sierra, had acquired a contrary habit, resembling a habit of gregarious birds and mammals. For this informing sound (unless it mimicked some _warning-sound,_ as of a rattlesnake, which it didn't) could not possibly be beneficial to individuals living alone, as grasshoppers generally do, but, on the contrary, only detrimental; and such a habit was therefore purely for the public good, and could only have arisen in a species that always lived in communities. On another occasion, in the middle of the hot season, I was travelling alone across-country in a locality which was new to me, a few leagues east of La Plata River, in its widest part. About eleven o'clock in the morning I came to a low-lying level plain where the close-cropped grass was vivid green, although elsewhere all over the country the vegetation was scorched and dead, and dry as ashes. The ground being so favourable, I crossed this low plain at a swinging gallop, and in about thirty minutes' time. In that half-hour I saw a vast number of snakes, all of one kind, and a species new to me; but my anxiety to reach my destination before the oppressive heat of the afternoon made me hurry on. So numerous were the snakes in that green place that frequently I had as many as a dozen in sight at one time. It looked to me like a coronelia--harmless colubrine snakes--but was more than twice as large as either of the two species of that genus I was already familiar with. In size they varied greatly, ranging from two to fully five feet in length, and the colour was dull yellow or tan, slightly lined and mottled with shades of brown. Among dead or partially withered grass and herbage they would have been undistinguishable at even a very short distance, but on the vivid green turf they were strangely conspicuous, some being plainly visible forty or fifty yards away; and not one was seen coiled up. They were all lying motionless, stretched out full length, and looking like dark yellow or tan-coloured ribbons, thrown on to the grass. It was most unusual to see so many snakes together, although not surprising in the circumstances. The December heats had dried up all the watercourses and killed the vegetation, and made the earth hard and harsh as burnt bricks; and at such times snakes, especially the more active non-venomous kinds, will travel long distances, in their slow way, in search of water. Those I saw during my ride had probably been attracted by the moisture from a large area of country; and although there was no water, the soft fresh grass must have been grateful to them.