It’s a song that fills the summer air. To a female cicada, it may sound sweet. To the rest of us, the noise can be deafening. By far the loudest noise produced by any insect, the mating song of the male cicada can be heard over the roar of a lawn mower. But for all their noise and rather large size (many species are more than an inch long), cicadas are actually harmless.

When periodical cicadas show up, they bring the whole family. Luckily with these particular cicadas, it only happens every 17 years.

Photo Credit: Dale Dykema

With their bright red eyes and reddish markings on their bodies, periodical cicadas look different than other cicadas.

Photo Credit: Dale Dykema

As periodical cicadas emerge from the ground, they leave pencil-sized exit holes. (Mother Nature’s way of aerating the soil.)

Photo Credit: Dale Dykema

This cicada has just emerged from its shell and will stay cream-colored until it dries.

Photo Credit: Dale Dykema

There are many different kinds of cicadas out there in the world – at least 2,500 species are known – and they vary in size and color. But one thing they all have in common is their long life cycle.

All cicadas have a life cycle longer than a year, and that cycle’s pretty simple: After mating, the females use a special blade-like appendage to create pockets in the newly grown limbs of many tree and shrub species, and then they lay several eggs in each hole. After four to seven weeks, the eggs hatch, and the tiny nymphs drop to the ground. They burrow underground in search of tree roots, and once a suitable root is found, the nymphs insert their piercing/sucking mouthparts and suck the juices right out of the plant.

Depending on the type of cicada, this feeding frenzy continues for two to five years. One group in particular – the periodic cicadas – stays underground and feeds for 13 or 17 years. When the nymphs mature, they crawl near the soil surface as it warms up in the spring. After leaving the soil, they crawl up the tree trunk, and adults crawl out of their nymphal skin, leaving it behind on the tree.

Cicadas can be heard every summer, but these are usually the non-periodic species, and their numbers are relatively few. But when the time arrives for an emergence of periodic cicadas, many more can be seen and heard. Then suddenly, the rather benign insects that we seldom notice become so numerous you can’t help but feel overwhelmed.

In the South, 13-year cicadas are most common, while the 17-year cicada is found in the North. There are several Midwestern locations that are dealing with emerging 17-year cicadas now, where seemingly endless numbers are leaving the soil in near unison and crawling up trees and shrubs. States blessed with this 2007 event include Illinois, Indiana, Iowa, Michigan and Wisconsin. In fact, this is such a huge event that there’s been considerable media coverage of this spring’s emergence of the 17-year cicadas in Chicago. But after this season, these locations won’t see periodic cicadas for another 17 years.

The emergence of 17-year cicadas will be even more widespread next year, invading yards in Georgia, Kentucky, Maryland, Massachusetts, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia. What’s interesting is that while widely distributed over the eastern half of the US, periodic cicadas aren’t found anywhere else in the world!

When a brood of cicadas emerges from the soil, they often fall prey to many animals. This is especially true during the emergence of periodic cicadas, when birds, rodents, snakes, lizards and fish take advantage of this plentiful food source. (I’ve even seen my dogs chow down on cicadas!) In many parts of the world, people harvest adult cicadas just after they emerge from their nymphal shell (when they’re the most tender) and cook them in different ways. (A quick search online will reveal many cicada recipes!)

Despite their large numbers, cicadas do very little damage to trees. In fact, feeding by the nymphs is considered to be “slightly damaging” at best. The only potential for harm is caused by the females when they split holes in the young twigs to lay eggs: The leaves on theses twigs may wilt and the twigs may die, but the tree won’t be harmed. The exception may be in fruit orchards, when limbs that could potentially produce fruit die and fall off the trees. Control is seldom needed, but if you have a prized small tree, a mesh barrier installed around the canopy can be used to keep egg-laying females away from new tree limbs.

Cicadas are pretty neat insects. Their long life cycle – and the fact that some only emerge every 13 or 17 years – has created great interest among entomologists and homeowners alike. They may be loud, but their song is very much a part of summer. And depending on where you live, that song may seem a little louder than usual this year, as the 17-year cicadas make their special appearance!