National Geographic : 1953 Jul
the female could not hear; recently they have found ears on her belly. But the purpose of the dismal drumming remains a mystery. Where cicadas abound, the racket may make daytime hours uncomfortable. Reports tell of schools being dismissed because youngsters could not study; of travelers who, upon enter ing infested areas, stopped their cars to see what was wrong with the motors; of conversa tion on village streets made impossible by the incessant roar. Yet so localized is the cicada's appearance that while one town may be hideous with noise, a near-by community may be virtually free. 17 Broods-One for Each Year Periodical cicadas appear somewhere in the United States every year, for there pre sumably are 17 broods of the 17-year race, each numbered in the order of its appearance. Some are small and scattered: Brood XI, due next year, has been recorded chiefly in the Connecticut River Valley, and it has been much reduced in numbers, possibly to the point of extinction. This year's crop, Brood X, is the largest and most widespread. Records since 1715 show it appearing from Vermont to central Georgia and from the eastern seaboard to the Mississippi, with an additional small colony on the Iowa-Nebraska border. This brood emerges most thickly in three well-defined regions: a group in Indiana and Ohio; one in New Jersey, eastern Pennsyl vania, Delaware, and Maryland; and a third covering the southern Appalachians in north ern Georgia, Tennessee, and North Carolina. We know by counting backward that Brood XIV is the one seen by the Cape Cod settlers in 1634; it next appears in 1957. Brood IV, the most westerly group, con centrates around the Kansas-Missouri-Iowa border region. Theoretically, there are 13 broods of the 13-year cicadas, one for each year, but only two are of notable size. This race appears chiefly in the Deep South, especially in the Mississippi Valley. Records show the broods, whether 17- or 13-year, appearing only in the United States and only in its eastern half. Thus the peri odical cicada is a North American insect-an American institution, if you will-although its steadily weakening numbers foretell a possible fate like that of another American, the pas senger pigeon. Cicadas mate a week or ten days after emerging. Within a few days the female be gins to lay eggs beneath the soft bark of twigs or plant stems. She prefers deciduous plants and rarely attacks conifers. Oak, hickory, apple, and peach are favorites.