{"id":2269,"date":"2012-04-01T20:51:50","date_gmt":"2012-04-02T03:51:50","guid":{"rendered":"http:\/\/www.cicadamania.com\/cicadas\/?p=2269"},"modified":"2024-08-17T12:50:20","modified_gmt":"2024-08-17T19:50:20","slug":"cicadas-and-prime-numbers","status":"publish","type":"post","link":"https:\/\/www.cicadamania.com\/cicadas\/cicadas-and-prime-numbers\/","title":{"rendered":"Cicadas and Prime Numbers"},"content":{"rendered":"

Last week io9 published an article titled Why do cicadas know prime numbers?<\/a> The gist of the article is that cicadas developed long, prime-numbered, periodical life cycles to avoid gaining a predator that can synch up with the cicadas<\/strong>.<\/p>\n

It’s an interesting read, but it’s a little thin on facts and references. Here is part of what the article is missing:<\/p>\n

Only seven out of the hundreds of species of cicadas have 13 or 17-year life cycles<\/strong>, and they all belong to the genus Magicicada. Three species of cicadas have 17-year life cycles: M. septendecim, M. cassini, and M. septendecula. Four species of cicadas have 13-year life cycles: M. neotredecim, M. tredecim, M. tredecassini and M. tredecula. These are the periodical cicadas Stephen Jay Gould wrote about. <\/p>\n

As one proof of the theory, there isn’t a wasp that specifically predates Magicicadas (the genus of cicadas with long, prime-numbered life cycles), but there is a Cicada Killer Wasp that predates Tibicen cicadas, which have shorter life cycles and emerge every year. <\/p>\n

Although no animal predator has figured out their 17 & 13-year life cycle, one life form has: the Massospora cicadina fungus. <\/p>\n

The book in which Stephen Jay Gould theorized about prime numbers and periodical cicadas<\/strong> is Ever Since Darwin: Reflections in Natural History<\/strong>. You can search through the book<\/a> in Google Book Search, or just buy a copy (if you’re interested). I think I paid a cent for my copy (used).<\/p>\n

Other species of cicadas also have life cycles of a prime number of years, but some do not. The Chremistica ribhoi<\/a> is known for four-year life cycles, which coincide with the Fifa World Cup (association football event). The Raiateana knowlesi of Fiji has an 8 year life cycle<\/a>.<\/p>\n

Not all cicadas are periodical cicadas; the vast majority of cicada species appear every year even though their life cycles are longer than one year. <\/p>\n

If you want to delve deeper into the subject of periodical cicadas and prime numbers, search for the paper Evolution of Periodicity in Periodical Cicadas<\/strong> by Nicolas Lehmann-Ziebarth et al. <\/p>\n

This image is meant to be funny, but it’s a bit misleading…
\n\"A<\/a>
\nIt’s likely that periodical cicadas are counting in units of 4. 4+4+4+1 = 13. 4+4+4+4+1 = 17. <\/p>\n

Prof. Douglas Galvao of the State University of Campinas has written a paper titled Emergence of Prime Numbers as the Result of Evolutionary Strategy. Download his paper from Cicada Mania.<\/a><\/p>\n

Notes:<\/p>\n