Periodical Cicadas (Magicicada: Hemiptera: Insecta)

"There are at least 13 broods of 17-year cicadas and five of 13-year cicadas; these broods emerge in different years, and have different geographic ranges. The 17-year cicadas are generally northern and the 13-year cicadas southern, but there is considerable overlap, and both life-cycle types may occur in the same woods (but would emerge together only once every 221 years). The emergence of some of the larger broods is a very striking event, as the insects in these broods may be extremely numerous. The large broods of 17-year cicadas that have occurred in central and southern Ohio in recent years appeared in 1970, 1973, and 1974"