THE PERIODICAL CICADA
scattering colonies farther west. Brood III, 1929, is mostly confined to Iowa, Illinois, and Missouri. The largest of the broods is X, covering almost the entire range of the seventeen-year race. This brood made its last appearance in 1919, and is due next, therefore, in 1936. The series of broods is numbered thus follows the successive years to Brood XVII, the last brood of the seventeen-year race, which will return next in 1943.
The small and uncertain broods of the seventeen-year race are VII, XII, XV, XVI, and XVII. The cicadas that emerge in the years corresponding with these numbers represent incipient broods, being probably the descendants of a few individuals that sometime became separated from the larger broods of the years preceding or following. One of the smallest of the seventeen-year broods is XI, but since its colonies occur in Massachusetts, Connecticut, and Rhode Island, it is likely that it was more numerous in individuals in former times than at present. The brood with the oldest recorded history is XIV. This is a large brood extending over much of the range of the seventeen-year race, with colonies in eastern Massachusetts on Cape Cod and near Plymouth, the emergence of which was observed by the early settlers probably in 1634.
The broods of the thirteen-year race are numbered from XVIII to XXX, Brood XVIII being that which appeared last in 1919. But there are only two important broods of this southern race, XIX, which emerged in 1920, and XXII, which emerged in 1924. In most of the other years the shorter-lived race is represented by only a few individuals that emerge here and there over its range; and none at all are known to appear during the years corresponding with the numbers XXV and XXVIII.
The Hatching of the Eggs
Five weeks have elapsed since the departure of the cicada swarms. It is nearly six weeks since egg laying
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