17-year periodical cicada has returned
It’s not often insects make news, but for weeks I’ve been hearing and reading about the imminent emergence of 17-year periodical cicadas. By the end of the month, they will be impossible to miss in parts of Ohio, West Virginia, southwestern Pennsylvania, and western Virginia. 2016 is an emergence year for Brood V of these fascinating insects.
Periodical cicadas spend most of their lives, from four to 17 years (depending on the species) underground.
The green dog-day cicadas we see every summer take just two to four years to mature, and broods overlap, so some emerge every year. These are the ones we hear droning on hot summer days.
The emergence of 17-year cicada is a much less frequent event. Within these long-lived periodical species, there are different broods identified by Roman numerals in specific areas, that mature on different schedules. Brood V, for example, is currently emerging in my neck of the woods. For details on cicada biology and emergence schedules, visit magicicada.org.
Twelve broods of 17-year cicadas are found throughout the Midwest and northeast.
Each brood matures in a different year. This means that there are five years out of every 17 when no 17-year cicadas appear. In the southern states, there are three broods of 13-year cicadas, so there are 10 periodical cicada free years.
Dog day cicadas are dark with black eyes, greenish markings, and can be nearly two inches long. Periodical cicadas are smaller, have black bodies, and bright red eyes.
Tales of the sheer numbers of periodical cicadas that emerge in brood years are legendary – tree trunks and patio furniture covered with shed skins and afternoon choruses that can be deafening.
While in the immature stage, periodical cicadas subsist by sucking fluids from the roots of trees. During that time, these nymphs grow from the size of an ant to adulthood. Several weeks before it’s time to emerge, nymphs dig exit tunnels to just below the surface of the soil.
When the soil temperature six to seven inches below the surface reaches 64 degrees F, most of the nymphs emerge within a period of just a few days. Because it has been so cool recently, the grand emergence has been delayed in many areas. As soon as it warms up, the onslaught should commence.
At dusk on the fateful night, nymphs will leave their burrows and crawl onto nearby tree trunks, stems, and fences. There they molt and leave behinds the brittle shed skins kids love to collect.
Newly emerged cicadas are white, moist, and soft. As they dry the body darkens and hardens. It takes three to five days for adults to fully mature. During this time, cicadas are entirely defenseless, but there are so many of them predators (from snakes and songbirds to turkeys, dogs, cats, and bears) cannot begin to eat them all.
After drying out, males begin singing to attract females. Male cicadas have special sound producing membranes on the first abdominal segment that vibrate above a hollow resonating chamber. Put tens of thousands of them in a backyard, and the chorus becomes deafening.
After mating, females use their ovipositor to slit tender woody twigs and lay as many as 20 eggs in each slit. Each female can lay as many as 600 eggs. When mating is complete after four to six weeks, adult cicadas die.
Some time in July, the eggs hatch and tiny nymphs drop to the ground, burrow into the soil, and find tiny roots to suckle. Four, 13, or 17 years later, a new brood will emerge.
Cicadas’ egg laying habits can damage tender twigs of small trees, but any harm is largely cosmetic. To protect favorite woody, plants cover with cheesecloth. Pesticides are not necessary.
Though cicadas have an alien-like appearance, they use the long piercing feeding tube only to suck plant fluids, and their ovipositor is used only to lay eggs. Cicadas do not bite or sting. They are harmless.
Pick up a cicada, and it may struggle, vibrate its wings, and buzz. But it’s all show. And the show lasts only through early summer.
Scott Shalaway can be heard on Birds & Nature from 3 to 4 p.m. Sundays on 620 KHB Radio, Pittsburgh or live online anywhere at khbradio.com. Visit his website drshalaway.com or contact him directly at firstname.lastname@example.org or 2222 Fish Ridge Road, Cameron, WV 26033.