May 03, 2004
Cicada Evolution
Today must be science day. As something of a followup to this post, here's an article about the evolution of Magicicada, periodical cicadas that emerge every 13 or 17 years.
(via The Loom)
I'm too lazy to get my book and look it up (anyway, I think I may have lent it to someone), but in The Blind Watchmaker, Dawkins discusses cicadas that swarm periodically (I think he talks about 7 and 11 years, but 13 and 17 work too). Anyway, his point was that these are prime numbers (natural numbers greater than one that are divisible only by 1 and itself), and thereby preventing its natural enemies from falling into rhythm with them.
Yeah, that's one of the points the article makes. It all has to do with probability of survival.
Oh, another point, the main reason the Magicicada genus emerges in large prime-number intervals has nothing to do with predators, but to avoid interbreeding with other cicada broods that have different cycles. Read the whole article, it's really fascinating stuff.