Genus Magicicada - Periodical Cicadas

17-year locusts, 13-year locusts. (Note that true locusts are grasshoppers.)

Magicicada W.T. Davis, 1925. (See Remarks for discussion of taxonomy.)

Presumably from Latin magi(s) more, to a greater extent, plus Latin cicada, a cicada or tree-cricket (1) (Latin Dictionary). (Most members of this genus were originally placed in Cicada Linnaeus, 1758.)

Checklist of Cicadas North of Mexico, and magicicada.org list 7 species.

17-year species:

13-year species:

See Remarks and Life cycle below on relationships among the 13-year and 17-year species.

Coloration distinctive: body black, red to orangish-red eyes, yellow-orange wing veins. Noted for mass-emergence of adults and the formation of choruses of singing males on a 17-year or 13-year period. Unmistakable as a genus--details of underside of abdomen (and male courtship song) can help identify species.

Eastern North America. 17-year broods are more northern (below, left), 13-year broods more southern (below, right):

  

Deciduous forests

Adults fly in late spring, typically late April to early June; generally earlier than other cicada genera.

Adults, as well as nymphs, feed on sap of deciduous trees.

Unique life-cycle, with almost all individuals emerging as adults after 13-year or 17-year period as nymphs. Members of a given brood in a particular area tend to emerge over a very short period, resulting in high population densities for a limited time. Males form huge "choruses" in deciduous trees--the numbers are so great that the noise can be painful to human ears.

There are four species with 13-year and three species with 17-year life cycles. The 13-year species are more southern, the 17-year species more northern. There are a number of broods, or "year-classes", whose members emerge in the same year in the same geographic area. (Specifically, there are currently 12 broods of 17-year cicadas, and 3 broods of 13-year cicadas, with some additional broods known historically that appear to be extinct--see magicicada.org.) Entomologists have a standard numbering system using Roman Numerals to designate these broods (Marlatt, 1907). A given brood typically contains members of all three species with the same life-cycle (13-year or 17-year). The brood populations appear to be relatively stable, and several have been tracked via historical records--in one case, (brood XIV, a 17-year brood) back to 1634 (Lyche, Periodical Cicadas).

There are various hypotheses for the length of the life-cycle (13 or 17 years). Prime number-based cycle may help the cicadas to evade tracking by cycling populations of predators and/or parasites. In addition, populations may converge on prime number-length cycles due to statistical effects (Cox and Carleton, 1998; Goles et al., 2001; Yoshimura, 1997).

There are three sets of sibling species within this genus, indicated by the species name suffixes: -decim, -cassini, and -decula. Each group has both 17-year and 13-year cycling populations, and these are traditionally treated as separate species. The closest relative of each Magicicada species is/are its relative(s) with the alternate life cycle (magicicada.org). The groups are:

An alternative interpretation of these relationships is that there are but three species (more-or-less) in the genus, with differing life-cycle forms for each. This is an ongoing area of research--see magicicada.org for a discussion.

The two -decula species seem to be much less common than the -decim and -cassini species.