A common creature in the portions of the desert in which cacti abound is the cactus rat, a small rodent about midway in size between the mouse and the ordinary rat. He is provided with a bushy tail which he carries over his back, squirrel fashion. He lives upon the barrel cactus, a plant so protected by spines as to seem unapproachable by man or animal. The cunning rat, however, has found a way of attacking this formidable vegetable. He burrows in the earth at the foot of the plant and comes at it from beneath. One specimen of the matured plant will keep a colony of the rats several months. They gnaw at its vitals till nothing but the empty shell remains, then they emigrate to some other plant and there set up housekeeping for another six or eight months. Living so far from a habitable country, the rat finds few enemies to molest it. The rattler is about the only creature which preys upon it, therefore it thrives and multiplies in the midst of the fearful region it has chosen for its home. It is astonishing to the desert traveler, after he has crossed half a hundred miles of parched and barren territory, to find about the spring of an oasis tortoises basking in the sun or swimming in the waters of the desert well. [Illustration: TARANTULA] The desert tortoise differs from the ordinary tortoise in several respects. It never exceeds in length over fifteen or sixteen inches, but in form and other characteristics it more nearly resembles the sea turtle than it does the tortoise. This leads to the belief that the desert specimen is the descendant of a sea turtle that throve in the waters of the gulf when it extended over the now desert country. Change of conditions from sea to land--and most forbidding land at that--is supposed to have dwarfed the original species till a new one is the outcome of the change. [Illustration: CENTIPEDE] If one familiarizes himself with the desert, he will find that the rattler and the Gila monster are not the only representatives of the "poison people" in that region. The scorpion, the tarantula, and the centipede make their home there and add to the dangers and terrors of desert travel. There are also animals found here and there in the desert and along its borders, which cannot be classed as typical desert animals. Bands of wild horses and wild burros are known to roam the formidable region, migrating from oasis to oasis, cropping the grasses at one place till they are exhausted, then moving across the burning sands, guided by unerring instinct, to the next green spot in the desert, twenty, forty, or perhaps fifty miles away. The coyote, too, finds his way to nearly all portions of the desert, and even in the midst of the great desolate waste his uncanny cry goes up in the night-time, making the darkness still more lonely for the chance traveler who pitches his tent in the land of terror. [Illustration: SCORPION]