Tuesday, May 10, 2011

Sweet Sounds of Springtime

Periodical Cicada. Photo by Susan Ellis Bugwood
One of my favorite things about summertime in the south is the humming and buzzing of cicadas.  The distinctive buzzing noise that fills the air across the south is the male’s mating call.   Right now, brood XIX of the periodical cicadas are waking up and preparing to swarm.  Brood XIX are periodical cicadas, meaning that all members of the brood emerge in the same year.  Brood XIX, also known as the Great Southern Brood, has been living underground since 1998.  This is the country’s largest brood, stretching across 12 states.

Every summer, the dog-day cicadas (Tibicen sp.) come out and fill the air with their mating calls.  These cicadas are larger than the periodical cicadas and have green markings.  The periodical cicadas are smaller, with hints of orange or red to their bodies.  This year, we will have the opportunity to see and hear both types of cicadas.  Periodical cicadas sing and fly in spring, whereas other species of cicadas are active during the summer.  

Cast "skins" and cicadas that were
unsuccessful emerging at base of tree.
Jordan Lake area. Photo by Steve Bambara
Both types of cicadas have a life cycle that takes them from tree to soil and back to tree again.  The life cycle of the Brood XIX periodical cicada takes 13 years to complete, while the speedy dog-day cicadas take only 2-5 years and are not synchronized with each other.  Several other broods of periodic cicadas emerge only once every 17 years!

After spending 2-17 years in the soil, cicada nymphs dig their way to the surface.  In late May or early June, the nymphs crawl to the trunk of a tree or some other tall object, and cling there.  Soon the insect molts into the winged adult stage, leaving behind the cast skin.  The shells left behind are fun to play with and also give back nutrients to the tree as they decay.

Cast skins clinging to sweet gum branch. Jordan Lake area
May 9, 2011.
Photo by Steve Bambara
Adults are active during the daylight hours.  Males begin to sing with a shrill buzzing noise to attract the females.  After mating, females used their sawlike ovipositors to split open the bark of hardwood twigs and insert their eggs.  After 6 or 7 weeks, the eggs hatch and tiny ant-like first stage nymphs drop to the soil to burrow for the next 2 or more years.  While in the soil, the nymphs feed on the roots of trees.
Split twigs showing egg deposits. Photo NCSU 

Aside from their daytime racket, the cicadas are otherwise harmless.  The only damage from cicadas occurs when they split tree twigs to lay their eggs.  This causes tip dieback (or natural pruning!), which is only a problem on a tiny tree. 

It is neither practical nor desirable to try and eliminate cicadas! They provide an abundant food source for local predators… a tasty buffet for birds.

Watch this neat video from Charlotte NC and hear the cicadas in action!

For more information: click here
Special Thanks to Stephen Bambara, NCSU Entomology for information and photos!