The Iowa Cicada

At www.physorg.com/print194880259.html … there is a story about the rare appearance of the cicada, an insect, in Iowa – that is supposed to appear at 17 year intervals. Why? I don’t know if this is one of those computer generated cycles based on the last few sightings, or not, but why would it appear at precisely 17 year intervals (unless that was the time it took to pupate) (?) Obviously, there is more to the research than the brief abstract describes but the last few occasions are dated 1963, 1980, and 1997 – and on that basis they should not reappear until 2014. I don’t know what the weather was like in Iowa on those years but in the UK 1962/3 and 1979/80 were exceptionally snowy, and if I remember rightly there was a volcanic eruption in 1996 (which may also have affected weather in Iowa). Is it a coincidence that 2009/10 was equally snowy – in the UK, at least.