Buzz readers east of the Mississippi will be thrilled to know that 2007 will see the emergence of the 17-year cicada. Experts are predicting May 22nd as the arrival date, at least in the Chicago area.
What are they?
Cicadas are a type of insect, known for their loud, insistent call. Although they are sometimes called the “17-year locust,” they are not locusts at all. Locusts are in the grasshopper family. Cicadas are related to aphids and leafhoppers.
In most species, adult cicadas only live long enough to mate and lay eggs on tree branches. When the eggs hatch, the nymphs drop to ground and start burrowing. They live by sucking juices from the roots of trees and shrubs. Once they develop, they emerge from the ground, molt, and fly off to mate, starting the cycle over again.
Most cicadas have a two- to five-year life cycle. But three species have an insanely long 17-year cycle. These are the ones due to hit the Midwest and northeast this year, and hit them hard. Remember last year’s
invasion of the box elder bugs? Well, you ain’t seen nothin’ yet! 17-year cicadas can emerge at rates of up to 1.5 million individuals per acre!
Do you mean why so many, or why every 17 years?
Why every 17 years?
Scientists speculate that this is a way to avoid predators. Many animals have multi-year life cycles, and predators sometimes evolve cycles that correspond with their prey. If a prey species has, say, a six-year cycle, then it can be eaten by all predators with a six-year cycle, a three-year cycle, or a two-year cycle. (The predators would of course have to eat other prey in other years.) But a prey species that evolves a life cycle based on a prime number – one that cannot be evenly divided by anything but itself – will avoid most predators.
OK, why so many?
This is another tactic for avoiding predators – or, more accurately, overwhelming them. With so many cicadas out and about, there’s no way the predators will be able to get them all. Some will survive long enough to reproduce, and ensure another invasion in 2024.
How do they all come out at the same time?
Temperature. When the ground reaches 64 degrees, they start digging their way out. Since they live off tree roots, you’ll find the largest numbers in forest preserves. Paved areas, or land that was farm or prairie 17 years ago, won’t produce any.
Ewww, they’re gross!
Yes, but they are utterly harmless. They have no jaws, so they can’t bite you, and they can’t eat your plants. (You might want to wrap young trees and shrubs to keep the eggs off, but mature plants will have no problems.) They’re not poisonous, so pets can munch on them. Just don’t let them eat too many.
I can also tell you from personal experience that they are excellent for teasing younger sisters with. Just make sure said sister doesn’t grow up to be extremely athletic and have a very long memory.
The Chicago Tribune has a good deal of cicada information:
A collection of links, including cicada exhibits, cicada music, and even cicada recipes! Yum!