The genus Magicicada contains the periodical cicadas, known for their 17- or 13-year synchronized life cycles and dense choruses. These cicadas have striking black bodies, red eyes, and red wing veins. Seven species are described from this group. Males and females join dense aggregations, or leks, where the males search for the stationary females using short flights and calls.
The songs and morphology of the seven periodical cicada species are described on pages linked below
Three 17-year cicada species exist, each with distinctive morphology (shape and color), behavior, and calling signals:
For each 17-year species, there is at least one morphologically and behaviorally similar species with a 13-year life cycle:
The closest relative of each Magicicada species appears to be a counterpart with the alternative life cycle. Some species pairs can be distinguished only by life cycle and geographic distribution. Some biologists have argued that the life cycle difference alone is not enough to justify species status. More information on the nature of the boundary between 13- and 17-year populations and the extent of hybridization between them would help to resolve this question, but for now there is no evidence that the distinctiveness of the life-cycle-forms is decreasing. For this reason and for practical purposes, most writers have adopted the taxonomy that recognizes the life cycle siblings as distinct species.
Most of the broods
contain all of the 13- or 17-year species, with a few exceptions. Brood VII contains only Magicicada septendecim (which tends to be found alone along the northern edge of the 17-year range), and 13-year Brood XXII lacks the new species Magicicada neotredecim. Also, the four 13-year species are all found together in only a limited portion of the 13-year range (see below for more on this and the range of Magicicada neotredecim).
Magicicada neotredecim was described in 2000 (see Evolution Vol. 54, No.4, Pp. 1313-1325). M. neotredecim and its closest relative, M. septendecim, are consistently distinguishable only in life cycle length. The new species is similar to 13-year M. tredecim, but distinguishable in male song pitch, female song pitch preferences (Marshall and Cooley 2000), abdomen color, and mitochondrial DNA (mtDNA) lineage (Simon et al. 1998, Martin and Simon 1988, 1990). These findings are consistent with the theory that M. neotredecim evolved from populations of M. septendecim by a life cycle change (Martin and Simon 1988, 1990, Marshall and Cooley, 2000, Simon et al. 2000).
The two 13-year -decim species have a special geographic relationship -- they are not sympatric (living together) across the entire 13-year range. Magicicada neotredecim inhabits the midwestern part of the 13-year range, while M. tredecim inhabits the southern and southeastern part. The two species overlap only along a narrow region in northern Arkansas, western Kentucky, and southern Missouri, Illinois, and Indiana. By comparison, the three 17-year species are found together from Connecticut to Kansas, and the remaining 13-year species together inhabit most 13-year populations. Where Magicicada neotredecim and M. tredecim overlap, male calling songs (and female song preferences) of these species have evolved to become more distinct. In this overlap zone, Magicicada neotredecim songs are much higher-pitched, while M. tredecim songs are slightly lower-pitched. This suggests that the songs have evolved to reduce wasteful sexual interactions between the species.