The Buzz On Cicadas

They lie underground for 17 years and suddenly, with unerring precision, burst forth en masse in late spring to mate in a buzzing cacophony

• Mark Cheater
• Feb 01, 2001

They lie underground for 17 years and suddenly, with unerring precision, burst forth en masse in late spring to mate in a buzzing cacophony. How do cicadas know when it's time to rise and shine?

Until recently, researchers thought cicada nymphs used internal clocks to measure the passing years while they nestled near tree roots. But entomologist Richard Karban at the University of California-Davis believes the creatures rely on trees to keep time for them.

To test his hypothesis, he transplanted 15-year-old cicada nymphs to new homes among the roots of peach trees, which he then forced (with artificially extended days) to flower twice each year instead of once. Most of these nymphs emerged from the ground a year early. This shows, Karban says, that "cicadas are using cues provided by their host trees to tell time."

Karban thinks the creatures monitor seasonal changes in the quality and quantity of root sap, on which they feed, to tick off the years. Although further work is needed to confirm this, Karban's study stands as a timely contribution to the field.