Very much like the spider-monkeys are the howlers, which are very common in the great forests of Central America. They owe their name to the horrible cries which they utter as they move about in the trees by night. You remember how the gibbons hold a kind of concert in the tree-tops every morning and every evening, as though to salute the rising and the setting sun. Well, the howlers behave in just the same way, except that their concert begins soon after dark and goes on all through the night. They have very powerful voices, and travelers who are not used to their noise say that it is quite impossible to sleep in the forest if there is a troop of howlers anywhere within two miles. And it is hard to believe that the outcry comes from the throats of monkeys at all. "You would suppose," says a famous traveler, "that half the wild beasts of the forest were collecting for the work of carnage. Now it is the tremendous roar of the jaguar, as he springs upon his prey; now it changes to his terrible and deep-toned growlings, as he is pressed on all sides by superior force; and now you hear his last dying groan beneath a mortal wound. One of them alone is capable of producing all these sounds; and if you advance cautiously, and get under the high and tufted trees where he is sitting, you may have a capital opportunity of witnessing his wonderful powders of producing these dreadful and discordant sounds." If one monkey alone is capable of roaring as loudly as a jaguar, think what the noise must be when fifty or sixty howlers are all howling at the same time. No wonder travelers find it difficult to sleep in the forest. Perhaps the best known of these monkeys is the red howler. Its color is reddish brown, with a broad band of golden yellow running along the spine, while its face is surrounded by bushy whiskers and beard. THE OUAKARI Another very curious American monkey is the red-faced ouakari. If you were to see it from a little distance you would most likely think that it was suffering from a bad attack of scarlet fever; for the face and upper part of the neck are bright red in color, as though they had been smeared with vermilion paint. And as its whiskers and beard are sandy yellow, it is a very odd-looking animal. If a ouakari is unwell, strange to say, the bright color of its face begins to fade at once, and very soon after death it disappears altogether.