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Cicada Facts: Understanding the Invasion

National Geographic News
Updated May 21, 2007
 
The billions of periodical cicadas of Brood XIII are expected to launch their invasion of northern Illinois and parts of Iowa, Wisconsin, Michigan, and Indiana this week (United States map).

Cicadas—insects that spend most of their lives as nymphs, burrowed underground and sucking sap from tree roots—emerge once every 17 years. Living fast and dying young, the shrimp-size, red-eyed insects transform into adults, reproduce, and die, all the while buzzing to beat the band.

Cicadas are often called locusts, but locusts are migratory grasshoppers that often travel in vast swarms. The appearance of cicadas in large numbers apparently caused the early European settlers in North America to equate them with the plague of locusts mentioned in the Bible.

• Periodical cicadas are found only in the United States east of the Great Plains. Seventeen-year cicadas are found mainly in the northern, eastern, and western part of their range. Thirteen-year cicadas predominate in the South. Within the 17-year cicadas there are 12 year-classes or broods.

• While different broods emerge in different years, there are some years in which there are no broods, the so-called empty-class years. Broods generally are geographically based, but there can be some overlapping. Some broods are found only in small areas. Others, like Brood XIII, can range across many U.S. states.

• Each brood of 17-year cicadas actually consists of three different species, and they all emerge together. The species look different from one another, and each one has its own song. Listen carefully and you should be able to distinguish the different choruses, according to experts. The three songs have been described as sounding like the word "pharaoh," a sizzling skillet, and a rotary lawn sprinkler. The different species sing at different times of the day—one favors the early part of the day, another prefers midday, and the third takes the late-afternoon shift.

Only the males sing. The females are lured to the sound and fly nearer. A female responds to a male with a flick of her wings. The two gradually draw close to one another until they meet for mating.

• In China male cicadas are kept in cages in people's homes so that the homeowners can enjoy the cicadas' songs.

• Cicadas may give away their pending emergence by building thousands of "chimneys" or "stovepipes" on the ground, especially near trees. They will emerge through these structures when they leave the ground and crawl up trees and shrubs.

• The transparent wings of cicadas are said to filter out ultraviolet light. People who have placed a cicada wing on their skin prior to exposure to the sun have noticed that they do not tan under the wing.

• Male cicadas die soon after mating. Females lay 400 to 600 eggs in as many as 40 to 50 different nests before they die.

Cicadas are said to make good eating because they are low in fat and high in protein. They are considered a delicacy by many people around the world. The European settlers in North America observed the Indians eating them. During the emergence of Brood X cicadas in 1987, a number of people in Cincinnati and Illinois were reported to have tried deep-fried and stir-fried cicadas. There was also talk of cicada pizzas and cicada candy, and local newspapers printed cicada recipes.

• Experts say that the best way to eat cicadas is to collect them in the middle of the night as they emerge from their burrows and before their skins harden. When they are in this condition—like softshell crabs—they can be boiled for about a minute. It is said they taste like asparagus or clam-flavored potato.

The animal world pigs out on the cicada feast. Particularly, songbirds make good use of the bonanza, and their young are well supplied with the nutritious insects. Moles are said to flourish on the fully grown nymphs in the weeks prior to emergence. Other wild animals that enjoy the advantage include snakes and spiders.

Dogs and cats may also avail themselves of the cicada smorgasbord. It does them no harm, although if they eat too many they may have some difficulty digesting a surfeit of cicada skins. There have been reported cases of dogs' digestive tracts becoming blocked by eating too many cicadas.

• Cicadas generally leave no lasting damage, except perhaps to young trees and shrubs. After they have bred and died, they leave the area littered with twigs and leaves that were damaged when the females laid their eggs. The remains of cicada bodies may lie so densely on the ground that there is a smell of decay, but the bodies provide good nutrients for the soil.

• Billions of cicada nymphs hatch in their nests high in the trees, drop to the ground, and burrow into the earth. There they find a succulent tree root, which they tap into with a special strawlike mouth part. They feed on the tree sap and pass through their various growth stages until, 17 years later, it is time to emerge and renew their life cycle.

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