Seven recognized species are placed within Magicicada—three 17-year species and four 13-year species.
These seven species are also sometimes grouped differently into three subgroups, the so-called Decim species group, Cassini species group, and Decula species group, reflecting strong similarities of each 17-year species with one or more species with a 13-year cycle.

Note that while the original and correct spelling for Fisher's 17-year species is cassinii, with two 'i's, a large majority of publications have spelled the name cassini since the mid-1960s.
 However, the original spelling has been maintained throughout by taxonomic catalogues, and the rules of nomenclature support the priority of cassinii (Article 33.4).
The correct spelling for the 13-year relative is tredecassini.
Seven recognized species are placed within Magicicada—three 17-year species and four 13-year species. These seven species are also sometimes grouped differently into three subgroups, the so-called Decim species group, Cassini species group, and Decula species group, reflecting strong similarities of each 17-year species with one or more species with a 13-year cycle.
Note that while the original and correct spelling for Fisher's 17-year species is cassinii, with two 'i's, a large majority of publications have spelled the name cassini since the mid-1960s.  However, the original spelling has been maintained throughout by taxonomic catalogues, and the rules of nomenclature support the priority of cassinii (Article 33.4). The correct spelling for the 13-year relative is tredecassini.
Periodical cicadas