The ticks inhabiting regions rich in bird and insect life, but with few mammals, are in the same condition as mosquitoes, as far as the supply of blood goes; and, like the mosquitoes, they are compelled and able to exist without the nourishment best suited to them. They are nature's miserable castaways, parasitical tribes lost in a great dry wilderness where no blood is; and every marsh-born mosquito, piping of the hunger gnawing its vitals, and every forest tick, blindly feeling with its grappling-irons for the beast that never brushes by, seems to tell us of a world peopled with gigantic forms, mammalian and reptilian, which once afforded abundant pasture to the parasite, and which the parasite perhaps assisted to overthrow. It is almost necessary to transport oneself to the vast tick-infested wilderness of the New World to appreciate the full significance of a passage in Belt's _Naturalist in Nicaragua,_ in which it is suggested that man's hairless condition was perhaps brought about by natural selection in tropical regions, where he was greatly troubled with parasites of this kind. It is certain that if in such a country as Brazil he possessed a hairy coat, affording cover to the tick and enabling it to get a footing on the body, his condition would be a very sad one. Savages abhor hairs on the body, and even pluck them off their faces. This seems like a survival of an ancient habit acquired when the whole body was clothed with hair; and if primitive man ever possessed such a habit, nature only followed his lead in giving him a hairless offspring. Is it not also probable that the small amount of mammalian life in South America, and the aquatic habits of nearly all the large animals in the warmer districts, is due to the persecutions of the tick?