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The article does a great job explaining why lifecycle periodicity is prime. But its very curious that 13 and 17 year cicadas are common, but not 7 or 11. Do suc

The article does a great job explaining why lifecycle periodicity is prime. But its very curious that 13 and 17 year cicadas are common, but not 7 or 11. Do such cicadas exists as well? Why do we not see cycles beyond 17 years?

pwg 5y ago
The article briefly touches on why not 7 or (almost) 11: "If we discount those cicadas with life cycles of ten years or fewer (as being too close to predator life cycles), we find that the most successful emergence rates for cyber cicadas are thirteen and seventeen years—precisely what we find in the wild." Why not beyond 17? The article does not say. The next prime would be 19 (only two years longer). Perhaps 17 provides a sufficiently large local optimum that there is little pressure to lengthen the cycle to 19 or beyond.
filoeleven 5y ago
The upper bound could be because it’s a long time to live as a glorified grub. It’s also interesting that the different periodical broods have pretty distinct boundaries: https://en.m.wikipedia.org/wiki/Periodical_cicadas#Map_of_brood_locations https://en.m.wikipedia.org/wiki/Periodical_cicadas#Map_of_br... Perhaps the same selective pressures that separated the broods geographically also filtered out shorter cycles due to predation?
abecedarius 5y ago
Also, is it known how they manage to count to 17? Are a noticeable fraction of them off by one?
- js2 5y ago
  > Sometimes periodical cicadas emerge “off-schedule” by one or more years. This phenomenon is often referred to by the general term “straggling,” although straggling cicadas can emerge either later or earlier than expected. https://cicadas.uconn.edu/broods/ https://cicadas.uconn.edu/broods/ https://cicadas.uconn.edu/stragglers/ https://cicadas.uconn.edu/stragglers/
  - abecedarius 5y ago
    Thanks. "Straggling emergences in which only a few cicadas are present are common, but larger unexpected emergences of thousands of individuals have also been reported." There's a suggestion that climate change may be causing more stragglers, but nothing else on how they count or time it.

pwg 5y ago

The article briefly touches on why not 7 or (almost) 11: "If we discount those cicadas with life cycles of ten years or fewer (as being too close to predator life cycles), we find that the most successful emergence rates for cyber cicadas are thirteen and seventeen years—precisely what we find in the wild." Why not beyond 17? The article does not say. The next prime would be 19 (only two years longer). Perhaps 17 provides a sufficiently large local optimum that there is little pressure to lengthen the cycle to 19 or beyond.

filoeleven 5y ago

The upper bound could be because it’s a long time to live as a glorified grub. It’s also interesting that the different periodical broods have pretty distinct boundaries: https://en.m.wikipedia.org/wiki/Periodical_cicadas#Map_of_brood_locations https://en.m.wikipedia.org/wiki/Periodical_cicadas#Map_of_br... Perhaps the same selective pressures that separated the broods geographically also filtered out shorter cycles due to predation?

abecedarius 5y ago

Also, is it known how they manage to count to 17? Are a noticeable fraction of them off by one?

js2 5y ago
> Sometimes periodical cicadas emerge “off-schedule” by one or more years. This phenomenon is often referred to by the general term “straggling,” although straggling cicadas can emerge either later or earlier than expected. https://cicadas.uconn.edu/broods/ https://cicadas.uconn.edu/broods/ https://cicadas.uconn.edu/stragglers/ https://cicadas.uconn.edu/stragglers/
- abecedarius 5y ago
  Thanks. "Straggling emergences in which only a few cicadas are present are common, but larger unexpected emergences of thousands of individuals have also been reported." There's a suggestion that climate change may be causing more stragglers, but nothing else on how they count or time it.