Decim periodical cicadas

Decim periodical cicadas is a term used to group three closely related species of periodical cicadas: Magicicada septendecim, Magicicada tredecim, and Magicicada neotredecim. M. septendecim, first described by Linnaeus, has a 17-year lifecycle; the name "septendecim" is Latin for 17. M. tredecim, first described in 1868, has a similar call and appearance but a 13-year lifecycle; "tredecim" is Latin for 13. M. neotredecim (Latin for "new 13"), first described in 2000 by Marshall and Cooley in an article in the journal Evolution, is a 13-year species but otherwise much more similar to M. septendecim than to M. tredecim as shown by studies of DNA and abdominal color variation by Simon and colleagues in a companion article in the same journal issue.

Like other species included in Magicicada, decim periodical cicadas have synchronized development with a long larval period underground (13 or 17 years, depending on species), followed by mass emergence, quick development to adult flying forms, and massed singing choruses of males that attract many females. Mating, egg-laying, and the death of all adult cicadas occur within weeks. Eggs hatch into first-instar larvae, which tunnel into the earth to begin their own multi-year subterranean feeding period.

All Magicicada species have a black dorsal thorax and orange wing veins. Their large compound eyes, and the three ocelli arranged in a triangle between two eyes, are red. All three decim species show orange coloration on the underside of the abdomen: broad orange stripes in the case of M. septendecim and M. neotredecim, solid orangish or caramel color in the case of M. tredecim.

Magicicada males typically form large aggregations that sing in chorus to attract receptive females. The decim periodical cicadas share a distinctive song said to resemble someone calling "weeeee-whoa" or "Pharaoh". The Encyclopedia of Entomology describes a decim song pattern as "pure tone, musical buzz ending in a drop in pitch".

The calling song of M. tredecim has a slightly lower pitch than those of M. septendecim and M. neotredecim. M. neotredecim was first identified when scientists noticed a bimodal split in the dominant pitch (frequency) of male calling songs during the 1998 emergence of Brood XIX.

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