Perhaps none of the bats is more seldom seen than this, for it cannot bear the light at all, and never comes out from its retreat until darkness has quite set in. And one very seldom finds it asleep during the day, for it almost always hides in dark and gloomy caverns, which are hardly ever entered by any human being. In France, however, there are certain caves in which great numbers of these bats congregate together for their long winter sleep. As many as a hundred and eighty of them have been counted in a single colony. And it is a very strange fact that all the male bats seem to assemble in one colony, and all the female bats in another. VAMPIRES In Central and South America, and also in the West Indian Islands, a number of bats are found which are known as vampires. Some of these eat insects, just like the bats of other countries, and one of them--known as the long-tongued vampire--has a most singular tongue, both very long and very slender, with a brush-like tip, so that it can be used for licking out insects from the flowers in which they are hiding. Then there are other vampires which eat fruit, like the flying foxes, about which we shall have something to tell you soon. But the best known of these bats, and certainly the strangest, are those which feed upon the blood of living animals. If you were to tether a horse in those parts of the forest where these vampires live, and to pay it a visit just as the evening twilight was fading into darkness, you would be likely to see a shadowy form hovering over its shoulders, or perhaps even clinging to its body. This would be a vampire bat; and when you came to examine the horse, you would find that, just where you had seen the bat, its skin would be stained with blood. For this bat has the singular power of making a wound in the skin of an animal, and sucking its blood, without either alarming it or appearing to cause it any pain. And if a traveler in the forest happens to lie asleep in his hammock with his feet uncovered, he is very likely to find in the morning that his great toe has been bitten by one of these bats, and that he has lost a considerable quantity of blood. Yet the bat never wakes him as it scrapes away the skin with its sharp-edged front teeth. Strangely enough, however, there are many persons whom vampires will never bite. They may sleep night after night in the open, and leave their feet entirely uncovered, and yet the bats will always pass them by. Charles Waterton, a famous English traveler, was most anxious to be bitten by a vampire, so that he might learn by his own experience whether the infliction of the wound caused any pain. But though he slept for eleven months in an open loft, through which the bats were constantly passing, they never attempted to touch him, while an Indian lad who slept in the same loft was bitten again and again.