Cordyceps Fungus

I found this post on the Discover blog via Metafilter. It's about the Cordyceps fungus. Too cool not to share!

Prime Numbers and the Magicicada

The Wikipedia entry on cicadas is a detailed and interesting read. One thing I find particularly compelling about cicadas is the habit of one genus of cicada to live and die in cycles of 13 or 17 years. This genus lives in North America and is known as genus magicicada or the "periodical cicada." Cicadas do not sting or bite, and have no known poisons or toxic chemicals. They are also tasty.
You may have noticed that the numbers of years of their life cycles are prime numbers. The hypothesis for why this is the case has to do with an adaptation that stifles predation. Cicadas, you see, have few natural defenses. They are slow walkers, slow flyers, and they don't make much of an attempt to escape when approached by potential predators. The only defenses they really have are to 1) overwhelm their predators with sheer numbers, and 2) live in 13 to 17 year cycles. They also spend most of their lives underground in the nymph stage living off of moisture from tree roots, generally only coming up to breed.

Since it is important for their survival that in a cicada population there be as many individuals as possible in a given community, they have to synchronize their development so that they all come out at once. Synchronized development can be maladaptive if say, your development is synchronized to a number of years or fractions of a year that are the same as, or natural divisors of predator development. Therefore cicadas emerge once every 13 or 17 years, thus providing them with the least possible contact with avian and insect predators.

This doesn't entirely prevent them from being eaten. In fact, most wildlife in the vicinity of cicada broods eat enough of them to become full. Their chitinous shells are made of long-chain polymers of glucose, so they're a quick source of protein. This only represents a small portion of the population though, so it's a net gain for the cicadas.

It might be nice to try some of theses cicada recipes:

Cicada Recipes

The Cicadas Are Coming!