From Nature Magazine, 20 May 2004, "Big Buzz as cicadas arrive after 17-year gap"
Researchers say that in some places there will be more than 370 noisy, colorful insects per square meter. The scene will be "like a science fiction movie," enthuses May Berenbaum, who is an entomologist at the University of Illinois at Urbana-Champagne... [...] ...But perhaps the most interesting question about cicadas is why they spend 17 years underground, a cycle that has been recorded since the mid-nineteenth century. Biologists think it is no coincidence that cicadas have evolved to reappear with periods that are large prime numbers. If the life cycle of a breed were 12 years, they speculate, it would interbreed frequently with others that had life cycles of 2,3,4, or 6 years. "The prime number prevents mating between two broods and hybridization,'' says Christine Simon, an evolutionary biologist at the university of Connecticut. There are 13- and 17- year broods, and these can only meet up every 221 years, giving them ample time to forge their unmistakable identities * * * * "So many cicadas, so few recipes" (I read that somewhere else, forgot where) Thane Plambeck 650 321 4884 office 650 323 4928 fax http://www.plambeck.org