Q&AZ: Why Do Cicadas Buzz?

By Claire Caulfield
Published: Monday, March 18, 2019 - 8:56am
Updated: Friday, April 19, 2019 - 1:30pm

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a photo of a bright orange and red insect
Charles Hedgcock/UA Dept. of Entomology
Okanaga rubrovenosa, literally meaning "the red-veined one from Okanaga Valley," is one of the most prominent cicada species found in the Southwest.

Arizona has more insect diversity than any other state — including four dozen different species of cicadas.

Best known for their loud buzzing in the summer, each species of cicada has their own unique call.

Scientists and cicada enthusiasts have creative ways to describe the different calls.

“Song sounds like rapid, raspy, clicks,” reads one.

“Call like someone repeatedly running a scissor over a grinding wheel,” reads another description.

KJZZ listener Paola wanted to know if those unique calls attract predators and asked via the Q&AZ reporting project.

That loud buzzing is a mating call made by male cicadas to attract a mate.

“They have structures on their underside called tymbals that vibrate and that vibration resonates and is amplified due to the the hollow abdominal cavity of the male,” said Gene Hall, manager of the University of Arizona insect collection. Hall also works with scientists to identify and catalog the millions of different insects in the region.

Hall said the insects evolved a unique cooling mechanism perfectly suited for the hottest part of the day — when most predators are sluggish.

“Cicadas have kind of like a natural evaporative cooling where they can remove the water from their blood and evaporate that through pores in their exoskeleton” said Hall. “It’s one of the reason why you hear them during the hottest part of the days during the summer.”

Halls also said that because their call is so loud, it can be hard for a predator to identify exactly where the call is coming from and “cicadas appear to have very good vision, and so if they feel they’re being targeted, they will stop making calls,” he said.

a cicada nymph
Charles Hedgcock/UA Dept. of Entomology
Cicadas spend their nymphal stage underground, munching on plant roots.

Cicadas are found all over the world and vary in size, eye color and markings. Cicadas are different from most other insects in two main ways: their mouths and their life cycle.

“They have a piercing and sucking mouthpart where a lot of other insects have chewing mouthparts,” Hall said. “And cicadas also go through an incomplete metamorphosis — egg to a nymphal stage to an adult stage, where as with other groups of insects, they go from egg to larval stage, a pupil stage and then the adult phase.”

Female cicadas lay their eggs on trees and, when the eggs hatch, the cicada nymphs burrow into the soil. They munch on plant roots and live underground for multiple years before emerging fully grown.

The cicada species found in the eastern United States are famous for emerging in large numbers every 13 or 17 years, but cicadas in the southwest only stay underground for 2-5 years, so at least one species of cicada will be active every Arizonan summer.

“This region of the Southwest, it’s home to such a wide variety of insects and other species and cicadas are just part of  the beautiful biodiversity of this region,” Hall said.

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