Extension Educator, Horticulture
Oh to hear the sounds of summer: chirping, buzzing, splashing, bellowing, thundering. Even the vociferous drone of cicadas is appealing compared to the sound of snow plows scraping highways.
Everything is big about a cicada. They have big bodies, big eyes and a big sound. Their portly bodies can get up to two inches long with green and brown or green and black markings. The adults have large clear wings. They do fly although not gracefully or for long distances.
The male cicadas "sing" to attract a female. Each species has a distinctive sound to attract the appropriate female. According to May Berenbaum in her book Ninety-nine Gnats, Nits, and Nibblers they don't really sing. The noise is produced by vibrating drum-like organs in the cicada's midsection. An accompanying air cavity makes a nice resonator to produce the male's vibrato to appropriately serenade his sweetie.
According to U of I Extension entomologist Phil Nixon and Extension educator Jim Schuster there are two types of cicadas commonly found in large numbers in Illinois. Dog-day or annual cicadas emerge every few years. Periodical cicadas emerge every 13 years in the southern half of Illinois and every 17 years in the northern half of the state. There are many different species of cicadas. Periodical cicadas are recognized by their red eyes and a black "W" marking on their wings.
The 17-year periodical cicada is set to emerge in northern Illinois in May of 2007. The fully grown nymphs emerge from the soil, climb a tree or other upright object, and shed the protective exoskeleton.
After mating, the adult periodical cicada female makes a slit in small twigs or small tree trunks to deposit her eggs. The eggs hatch and the young nymphs fall to the ground and tunnel down through the soil to feed on sap of tree roots until they emerge 13 or 17 years later.
Cicadas are amazing in their long life cycle and for their huge population. During the 1956 emergence there was anywhere from 1½ million cicadas per acre in forested floodplains to 133,000 per acre in uplands. Their nightly noise can be a nuisance. However, when the cicadas start dying and dropping from the trees the large numbers on the ground and the odor from their rotting bodies is memorable. In 1990, people in Chicago reported having to use snow shovels to remove the dead cicadas.
Cicadas are often mistakenly called locusts which are known for bringing on Biblical catastrophes. Locusts are really a type of grasshopper known for its voracious appetite for plants. Amazingly for their number, cicadas do little damage.
Although their feeding on tree roots for 13 or 17 years is not great for the tree, they do not cause enough damage to justify control. The egg-laying slit may cause the affected twig to dry and break off. This damage is also not harmful enough on an established tree to justify control. However, small transplanted trees, particularly fruit trees, commonly have a trunk diameter small enough that egg slits made in the trunk, may result in the tree snapping off.
To protect small trees from serious damage in a heavy emergence area cover trunks with screening or other material. In heavy emergence areas planting numerous small trees should be delayed a year or plant larger trees, preferably with trunk diameters of at least 2 ½ inches.
Keep in mind that immature periodical cicadas require a steady supply of sap-supplying tree and shrub roots for 13 or 17 years. Few cicadas would be expected in areas disturbed by housing developments, farm fields or prairie due to the lack of trees. Plus many predators love to eat them.
For more information on cicada life cycles and predicted emergence visit http://web.extension.uiuc.edu/cicadas/