Tuesday, June 24, 2008

Locusts

Do you know about locusts? As a kid did you look with wonder at their shells in your yard? Wait a minute; those weren’t locusts. Those were cicadas.

So, if those weren’t locusts then exactly what is a locust? Locusts are “mysterious creatures, whose sudden irruptions are their defining attribute. In biological terms, a locust is a type of highly mobile grasshopper with the capacity to attain enormous population densities and a proclivity for aggregating and traveling in bands [as immature nymphs] and swarms [as winged adults].” There are only ten species of locusts. [1]

Which one of these ten species of locusts ravaged the central part of the United States in the 1870s? You have heard those stories, right? If you have any locust stories in your family oral history please share them by clicking on the comment button below.

Cicadas are stumpy, clear-winged insects that resemble large aphids. Cicadas are in an entirely different insect order from grasshoppers and locusts. The misnaming of cicadas as locusts began in the 1600s and continues to today. Cicadas lay their eggs on plants while locusts lay theirs in the soil. Cicadas live below ground as nymphs while locusts live above ground. Cicadas feed sparingly as adults while adult locusts devour everything. Cicadas live in the vicinity of where they emerge while locusts migrate in swarms.[2]

A cicada is an insect with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the globe, and many remain unclassified.

Cicadas live in temperate to tropical climates where they are among the most widely recognized of all insects, mainly due to their large size and remarkable acoustic talents.

Cicadas are sometimes colloquially called "locusts," although they are unrelated to true locusts. They are known as "dry flies" because of the dry shell they leave behind. Cicadas do not bite or sting, are benign to humans, and are not considered pests.

The cicada grows up to three inches. Cicadas suck juice from tree roots when they are larva. Once the female cicada comes above ground, she mates. Then she lays her eggs and dies. The cicada can lay four hundred to six hundred eggs. The adult cicada lives in trees. Adult cicadas live for thirty to forty days. A cicada can chirp so loud you can hear it from half a mile away. A male cicada abdomen has two drum like sound chambers.

There are two main kinds of periodical cicadas in the United States. One kind spends 17 years as a nymph feeding on tree roots while living below ground, and the other lives underground for 13 years. Then each type, as if on some signal, emerges at the same time from the ground. They change into adults, lay eggs, and after a few weeks, they die. We don't see the next generation until 13 or 17 years later.


But don’t we see and hear cicadas every year? How do you explain that?


[1] Lockwood, Jeffrey A. 2004. Locust. New York: Perseus Books. Page 27.
[2] Lockwood, Jeffrey A. 2004. Locust. New York: Perseus Books. Page 28.

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