SOMERSET, Pa. — They'll be back. In huge numbers.
Sometime this spring — and no one is certain exactly when and where — a swarm of cicadas known as Brood II is expected to surface.
Cicadas follow a 17-year life cycle. The last major swarm, Brood X, surfaced in 2004. There are also annual cicadas and periodical cicadas. Cicadas look like gigantic flies. Entomologists think they are beautiful.
"This will be such an event," Sam Droege, an entomologist at the U.S. Geological Survey Patuxent Wildlife Research Center in Beltsville, Md., said in a telephone interview. "They are really pretty. They have wonderful red eyes. They are giant little flying machines. We learn so many interesting things from insects."
The Cicada Mania website map shows that the main swarms won't reach Somerset County. They will be concentrated primarily in Maryland, Virginia and eastern Pennsylvania. The website's slogan is "Keep calm — they're only 17-year cicadas."
Cicadas are insects best known for the sounds made by males. The males make this sound by flexing their tymbals, which are drum-like organs found in their abdomens. Small muscles rapidly pull the tymbals in and out of shape — like a child's click-toy. The sound is intensified by the cicada's mostly hollow abdomen. Female cicadas also make a sound by flicking their wings, but it isn't the same as the song cicadas are known for.
"Although cicadas may be intimidating with their large size and striking red eyes, the good news is they do not pose any health threats to humans," Missy Henriksen, vice president of public affairs for the National Pest Management Association, said in a telephone interview. "The bad news is these pests can appear in the hundreds of thousands per acre and quickly become a nuisance."
Her advice is to let people know that cicadas are not a cause for concern, they are a reason to wonder. They survive underground for 17 years, then emerge to mate before dying. They don't carry disease and they won't cause significant property damage except possibly to young trees.
"Understand if you are planning a spring wedding or other outdoor activity, you could have unexpected guests," Henriksen said. "It may be appropriate to have a backup alternative — the noise volumes reach 90 decibels. Consider an indoor backup plan or hand out earplugs as party favors."
Comparatively, 90 decibels is the volume of a motorcycle about 25 feet away.
This will be the first cicada emergence since Facebook and Twitter became popular, so expect this year's arrival to be accompanied by videos and tweets. It may get noisy and will disrupt outdoor events. The coming frenzy will last up to six weeks. It can start as early as late April and as late as early June.
Female cicadas place eggs on thin tree limbs. Six to eight weeks later nymphs hatch and burrow their way to tree and plant roots where they suck the juice. Each female can lay between 400 and 600 eggs, meaning populations can be enormous.
Droege said the dead, rotting bodies of the cicadas have a large nutrient impact on forests and streams. Cicadas themselves are not destructive. They do not strip foliage as do gypsy moth caterpillars. They are not locusts, which are grasshoppers.
"They are incapable of biting; they won't hurt you," Droege said. "These events in nature you can witness without turning on National Geographic. Go outside and enjoy nature. This only happens every 17 years."