by Dee Newman
Earlier this month millions of 17-year periodical Cicadas began to emerge from the earth here in middle Tennessee and northward. Four or five days after their emergence, the males started “singing.”
Their high-pitched, courtship cacophony serves as a mating call to attract females. It is produced by two drum-like membranes on the side of their abdomens.
Once mating has been accomplished, the females begin laying eggs. They have a knife-like ovipositor they use to slit the twigs of trees and other woody plants. In each slit, the female lays around two dozen eggs and then she moves forward to cut another slit and deposits more eggs. Each female can lay a total of 400 to 600 eggs.
Adult cicadas live for only four to five weeks. Their eggs hatch in six to seven weeks. The newly-hatched white, ant-like nymphs then drop to the ground and work their way into the soil until they find a suitable root to suck on. They grow very slowly. And no, their feeding seems to have no noticeable effect on the trees.
According to the University of Tennessee’s Agricultural Extension Service there are two races of the periodical cicada. One with a life cycle of 13 years which is common in the southeastern United States and one with a life cycle of 17 years which is generally more northern in distribution. Due to Tennessee’s location, both the 13-year and 17-year periodical cicadas occur in our state. There are also various populations (called broods) that emerge at different 13- or 17-year intervals.
In May, seventeen years from now, the nymphs will, once again, burrow upward and leave the soil. The emergence usually occurs after sunset. The nymphs will seek upright structures on which to molt.
The new adults will emerge several hours later. They are, at first, soft and white but become harder and darker in a short period of time. Adults then take flight, and their life cycle continues.
Though we may find their mass emergence a nuisance, scientists say: it aerates the soil, provides a banquet to thousands of predators, trims the tops of trees, and provides a needed burst of nutrients into the environment.