To: WSFAlist at WSFA.org
Date: Sat, 15 May 2004 02:52:07 -0400
Subject: [WSFA] Cicadas and prime numbers
From: ronkean at juno.com
Reply-To: WSFA members <WSFAlist at WSFA.org>

On Fri, 14 May 2004 12:53:18 -0400 (EDT) "Keith F. Lynch"
<kfl at KeithLynch.net> writes:

> I too wonder what Steve means by an area being less than 17 years
> old.
> There are plenty of places with buildings on now them that had no
> buildings on them 17 years ago.  But so what?  Cicadas aren't
> indoor
> creatures.
> --

These cicadas spend most of their lives two or three feet beneath the
surface, sucking on tree roots (according to a recent news article).
Construction which disturbs the earth likely kills cicadas at the
affected spots, and in any case paving or building over the places where
cicadas live prevents those cicadas from emerging, since they can't
burrow through asphalt or concrete.  Even adding fill dirt might prevent
them from emerging.

Cicadas will emerge at places where trees or bushes were 17 years ago,
even if the same trees are not still there now, if they have been able to
find some roots from which to feed, and if their emergence is not
otherwise blocked, and if they have not been killed in the meantime.  So
there are reasons why cicadas would be expected to be less plentiful in
areas where there has been construction during the past 17 years, but
some cicadas might still be able to emerge in those places.

Sometimes, when digging, I have encountered creatures which were probably
cicadas, though at depths of less than two feet.

There are 13 year cicadas, and 17 year cicadas.  Why are cicada cycles
always prime numbers of years?

Ron Kean

.

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