There are seven species of periodical cicadas. These are most easily distinguished by the very specific male call. Each species has as its closest relative a species with the alternate lifecycle. While it may be that in fact these are not actually seven distinct species, they are considered as such until more data comes in to resolve this question.

13-year cicada species:
• Magicicada tredecim (Walsh and Riley 1868)
• Magicicada neotredecim (Marshall and Cooley 2000)
• Magicicada tredecassini (Alexander and Moore 1962)
• Magicicada tredecula (Alexander and Moore 1962)
17-year cicada species:
• Magicicada septendecim (L. 1758)
• Magicicada cassini (Fisher 1851)
• Magicicada septendecula (Alexander and Moore 1962)

Magicicada septendecula is usually smaller and less common than the other two 17-year cicada species. Its song is also rhythmically distinct from the other two 17-year species. It is thought to be most closely related to the 13-year cicada M. tredecula.

(Cooley 2011; Cooley and Marshall 2011; Hill and Marshall 2011; Simon 2011)