Cicadas In Song

We are hearing a lot of buzzing in our backyards right now.  The sound is coming from one of the loudest insects found anywhere in the world, cicadas.  Cicadas are members of the family Cicadidae, and are they close relatives of leafhoppers.  Sometimes misnamed as locusts, cicadas are non-jumping insects not at all related to either locusts nor grasshoppers.  There are over 150 species of cicadas in the U.S., with about 12 occurring here in northeastern Illinois.  The cicadas we see and hear are all adults; some are species that we see every year, and some are species known as “periodic species” that only appear every thirteen or seventeen years.

Species seen each year usually live underground for two to four years with some portion of the population emerging every year as adults.  Periodic species will live either 13 or 17 years underground and all of the population will emerge together in one year.  After emergence, adults go through one final molt to climb out of their old skin, pump blood into their wings and then let the wings dry and harden.

During this time, we may see hundreds of empty skins hanging from plants only to fall off and decompose.  Adults will then mate, lay eggs, and die.  Eggs are placed in holes or slots cut into tree limbs by the adult female.  They hatch after a few weeks, and the young crawl to the edge of the branch and drop off into the soil below.  They burrow their way underground and attach themselves to tree roots, where they will live until adulthood by sucking on tree sap.  A large population of individual cicadas living in a specific location is called a brood.  Twelve different broods of 17-year cicada species and three broods of 13-year cicada species have been identified throughout the eastern half of the United States.  In addition to a unique location, each brood emerges in a different year. 

Each species of cicada has its own distinct song, but all cicadas create their sound from a unique pair of organs called tymbals.  They are located on either side of the abdomen and consist of a membrane stretched across ribs.  As muscles contract, each rib buckles against the membrane with a snap.  A special air sac located in the same area amplifies the sound.  A cicada can perform this action several hundred times per second, and the resulting sound is a loud buzzing that can be heard for long distances. 

Cicadas are daytime singers and each species sings in a particular portion of each day.  In most species, only the males sing, and they start with a calling song, trying to attract a female.  When an interested female comes close, she will signal her presence with a snap of her wings.  Once the male hears her, he will change his song to a courtship tune that attracts her further and has her snapping her wings more vigorously.  This helps to guide the male to her and after locating her he will sing a third tune, a mating song.  

I encourage you to listen for the different songs sung by the male throughout the courtship proceedings as well as different songs from the three to four species currently active in this area.