One of the world's most mysterious insects is about to invade the skies over western Pennsylvania, but an expert in Penn State's College of Agricultural Sciences says it's not a cause for serious alarm.
Residents of Adams, Bedford, Berks, Blair, Centre, Clearfield, Clinton, Cumberland, Franklin, Huntingdon, Lackawanna, Lehigh, Luzerne, Lycoming, Mifflin, Montour, Northumberland, Perry, Potter, Schuylkill, Snyder, Tioga, Union, and York Counties soon will see an emergence of periodical cicadas, commonly but mistakenly called 17-year locusts. "These insects are harmless to people, but they can damage shade trees, fruit trees or high-value ornamentals," says Penn State Extension entomologist Gregory Hoover.
Damage caused by periodical cicadas occurs during egg-laying. Using the blades of a saw-like device on her abdomen, a female will cut several small pockets in the bark of a twig before depositing 400 to 600 eggs. This process can cause small limbs or seedlings to wilt and may provide an opening for disease. Adults live only a few weeks, but the twig injury they cause may be apparent for several years.
When the time is right, usually in late May or early June, the nymphs exit the soil through half-inch holes and climb a foot or more up trees or other objects. Within an hour, they shed their nymphal skins and become adults.
Adult cicadas are clumsy flyers, often colliding with objects in flight. Males begin their constant singing shortly after they emerge, but the females are silent. When heard from a distance, the cicadas' chorus is a whirring monotone, sometimes described as eerie-sounding. On rare occasions when an adult eats, it sucks fluid from small twigs but does not feed on leaves. Ten days following emergence, mating takes place.
Adults live up to four weeks above ground. Six to seven weeks after the eggs are laid, the nymphs hatch and drop to the ground. There, they enter the soil, not to see the light of day for 17 years.
For a free fact sheet on periodical cicadas, visit the Web at: