JULY
1999

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

7-22-99

The Treetops are Alive with the Sounds of Cicadas

As has been the case for many millennia, summer brings the sound of cicadas. Cicadas are members of the insect order Homoptera. This order includes plant hoppers, leaf hoppers, whiteflies, scale insects and aphids.

Most people recognize these insects as pests. And many Homoptera do damage plants by feeding on plant sap and sometimes transmitting plant diseases.

Homoptera generally are small insects. Cicadas are an exception. They range in size from one to two inches in length.

Cicadas are well known because of their sound production. Two organs on the abdomen are used to create sounds. Each organ includes a membrane and a ribbed structure called a tymbal. When the tymbal is vibrated by strong muscles, the “song” is produced and amplified by the membrane.

Cicada songs are produced only by males. The male sings to attract the female of the species. Each type of cicada has a specific song, but to humans, most of the songs can be described as a buzz. When many cicadas are singing in unison, the buzz can become quite annoying—and loud! So loud that some folks have described the music as a deafening racket.

Regardless of the human perception of the quality of the sound of cicadas, their singing certainly attracts attention. Some authorities hold that the grasshopper in Aesop's Fable of the grasshopper and the ant actually may have been a cicada in the original tale. Both insects were well known to ancient peoples. Both grasshoppers and cicadas emerge in large numbers and produce sound. And essential to the fable, neither insect plans for the winter.  At least by laying in food as do the ants.

Confusion between cicadas and grasshoppers has occurred several times throughout recorded history. Such confusion occurred in North America when the first European settlers arrived. They encountered great emergences of cicadas and called them locusts, the name commonly used in other parts of the world for migratory grasshoppers. As a result, in the United States, we frequently refer to cicadas as locusts.

By either name, locust or cicada, the insect fascinates us as much as it did people in Aesop's day. Biologically, the life cycle is interesting. The adult female lays eggs in slits under the bark of the twigs of trees. The eggs hatch and the young cicada drops to the ground where it crawls into the soil. In the soil, it feeds on the roots of trees.

After its immature stage is complete, the cicada crawls out of the soil, mostly during nighttime hours. From there, it climbs up tree trunks, sides of houses or fence posts where it attaches and emerges from its immature skin. The skin, called a shell by many people, is left for children to collect.

Cicadas, depending on species, spend anywhere from 1 to 17 years underground during the immature stage. The species with the 17-year life cycle are known as periodical cicadas. There are also periodical cicadas with a 13-year life cycle. Either way, the periodical cicadas have the longest life cycle of any insect, except the termite queens of Africa.

The emergences of periodical cicadas sometimes results in millions of the adults present at the same time.  Under these circumstances, the trees are literally alive with flying and singing insects. Native Americans were well aware of the singing cicadas. But these resourceful people enjoyed more than the song of the insect. Many Native Americans collected cicadas as they emerged from the soil, roasted them over a fire and ate them. For them, it was a delicacy complete with dinner music, provided by the delicacy!

 

Writer: Tom Turpin
Editor: Olivia Maddox