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The Dog-Day Cicada (Tibicen canicularis)

Annual Cicadas

The cicadas you hear in the late summer are all annual cicadas and are easily differentiated from the periodical cicadas that emerge in large numbers in the spring by their loud rising buzz. In Northeastern Wisconsin the cicada most often heard in the afternoon is Tibicen canicularis. These, and about 7 of the 9+ species found in Wisconsin are commonly called annual cicadas because even though they have 2-4 year lifecycles, adults emerge every year because the broods are not synchronized. Cicadas songs sound similar to those of katydids and crickets (family Orthoptera), however, cicadas are in the family Homoptera and are closely related to aphids and leafhoppers.

Only male cicadas produce their amazing song and they do it through a mechanism found in no other insect. Crickets, katydids, and grasshoppers rub their wings or legs against their bodies in a process called stridulation. Cicadas are able to create a much louder sound through a pair of abdominal organs called tymbals. Each tymbal is a ribbed membrane located just below the wing base that can be deformed by a pair of powerful of superfast abdominal muscles. The loud buzz we hear occur as each the ribs of the tymbal are pulled into the abdominal cavity it produces a resonant pulse of sound. The exact mechanism is complex and scientists are still trying to reduce the buzz to its individual components, but it amounts to an incredibly loud superfast clicker.

This method is so effective that some large Australian cicadas can produce noise at levels close to the human pain threshold of 120 db and are the loudest insects in the world. Sanborn and Phillips (1995) found that loudness (sound pressure) in cicada calls is directly related with insect body mass. The loudest cicadas are also the largest. Tibicen walkeri, a cicada found in the southeastern United States, is the current US record holder at 108 dB. However, larger cicadas exist in Southeast Asia that have not yet been tested and are most certainly the loudest in the world.

Scientists disagree about why the song is so loud. It certainly allows males to call in females from a long distance away. Cicadas also use the tymbal to produce an alarm call and some scientists believe that the loud sound scares away potential predators like birds. Scientists at the University of Connecticut studying cicada mating behavior have shown that females choose males based on the quality of their songs and males change their songs in response to female behavior. They have also shown that males can change their call to distract females responding to the calls of nearby males.

Cicada Resources

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Last updated on April 15, 2014