There are only four poisonous snakes native to the United States. Three of these are pit vipers-the rattlesnake, the copperhead, and the cottonmouth moccasin. The fourth is the brightly banded coral snake. / The thousand people huddle inside a wall which encircles low, flat-roofed houses built of bakes mud. Dust, inches thick, is stirred up by the camels and donkeys as they move through the town. For six months in the year it never rains:120 degrees in the shade is not uncommon.