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Background Information
The periodical cicada, Magicicada species, has the longest developmental period of any insect in North America. There is probably no insect that attracts as much attention in eastern North America as does the periodical cicada. Their sudden springtime emergence, filling the air with their high-pitched, shrill-sounding songs, excites much curiosity. 
Two races of the periodical cicada exist. One race has a life cycle of 13 years and is common in the southeastern United States. The other race has a life cycle of 17 years and is generally more northern in distribution. Due to Tennessee’s location, both the 13- year and 17-year cicadas occur in the state. Although periodical cicadas have a 13- or 17-year cycle, there are various populations, called broods, that emerge at different 13- or 17-year intervals.
Fifteen broods have been described by scientists and are designated by Roman numerals. There are three 13-year cicada broods (XIX, XXII and XXIII), and 12 of the 17- year cicada broods (I-X, XIII and XIV). Also, there are three distinct species of 17-year cicadas (M. septendecim, M. cassini and M. septendecula) and three species of 13-year cicadas (M. tredecim, M. tredecassini and M. tredecula). In Tennessee, Brood XIX of the 13-year cicada had a spectacular emergence and is expected to re-emerge in 2024. In 1987, Brood X of the 17-year cicada emerged across the state and did the same in 2004. Brood X is expected to re-emerge in 2021. Brood X has the largest emergence of individuals for the 17-year cicada in the United States. Brood XXIII of the 13-year cicada emerged in May 2015
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Information and Images provided by: Dr. Frank Hale (UTK)