Friday, August 4, 2017 1:12 PM
We have been getting calls in our diagnostic center from people trying to identify these beetle like insect shells they are finding in their yards and wanting to know what that very loud sound is coming from their trees. The shells and the sound are from cicadas and if you aren’t from Oklahoma, the sheer volume of noise a tree full of cicadas are capable of generating can be a little unnerving. But for locals, it reminds us summer is here.
There are several types of cicadas. The species we are most familiar with is called the Dog-Day Cicada. These cicadas typically have a life cycle of between 2 and 5 years. The sound you hear coming from the trees is actually the male cicada singing to attract females. The males produce this sound by rapidly beating their wings against their abdomen. On each side of the abdomen there is a specialized organ called tympana, which helps to increase the sound of this beating considerably. These mating calls have been recorded as loud as 108 decibels, which is approximately the same sound level as an automobile horn from about 3 feet away.
Once the male’s singing has attracted a willing partner, the female cicada lays her eggs into twigs and small branches using a somewhat saw like egg laying structure called an ovipositor. 6 to 7 weeks later the small nymphs hatch and drop to the ground. They then burrow into the soil, sometimes several feet deep, where they live out the majority of their lives growing through several growth stages called instars.
When they are ready, the fully developed cicada nymphs burrow out of the ground at night, leaving an exit hole about the size of a nickel. Once out, they climb up onto a tree, fence, or low plant where the adult cicada emerges from its final nymph stage leaving that light brown shell or exoskeleton we are familiar with behind. These adults can live 5 to 6 weeks during which the process of finding a mate begins once again.
Oklahoma is home to at least 12 species of cicadas, one of which is a periodical cicada whose life cycle is an impressive17 years. This is the longest life cycle of any known insect. Most periodical cicadas in Oklahoma belong to what biologists call brood IV and were active in 1947, 1964, 1981, 1998, 2015 and will be back in 2032.
Both the nymphs and adults suck sap from trees but typically cause very little damage. They are no danger to our vegetables or flowers.