The District Vet: Cicadas Return

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Three years ago, the Northeast experienced trillions of cicadas emerging from the ground. In suburban and wooded areas, the ground was covered in chitinous brown shells, with an incessant siren-like wail in the background. This was Brood X of the 17-year periodic cicada.

Of the 3,000+ known species of cicada, periodic cicadas emerge all at once, every 13 or 17 years, and annual cicadas emerge every year. This year, two large broods will be emerging in the Midwest and Southeast, just missing the District. Your ears will be thankful. Residents of Illinois will have a loud summer.

Before reading further, it is important to note that cicadas, although resembling small flying tanks, are not dangerous. They lack biting mouthparts and do not sting. They are not toxic, although you probably should not eat them. We know your dog will ‒ but no significant danger aside from possible intestinal upset. That doesn’t mean your dog should go on the cicada buffet: too many can cause a possible intestinal blockage. Your biggest danger is being hit in the face by an errant cicada on its merry way to a different tree.

Whereas female mosquitoes bite, male cicadas are responsible for most of the noise disturbing your afternoon nap. After a number of years underground, once the ground warms to 64 degrees, cicadas make their way to the surface from subterranean burrows. Emergence occurs over approximately two weeks, with the adult  living for only four to six weeks. During this period the cicadas must mature into adults, find the mate of their dreams and lay their eggs on trees. Then they die.

Be nice to them. They just spent years underground only to be in the sun for about a month.

To woo a female cicada, the male starts to “sing” a week or so after crawling out of the ground. He climbs up a tree, molts, spread his wings and hardens his shell. By vibrating tymbals ‒ special ridges on his thorax ‒ 300-400 times per second, he can make a loud call audible over great distances. When the sounds of many neighboring cicadas synchronize, the volume can approach 100 decibels and sound like a car alarm. The calls are also used to mark out territory. The boys are not totally to blame for the cacophony: female cicadas can make clicking sounds with their wings to attract a mates.

Although lacking chewing mouthparts, adult cicadas feed on trees and shrubs. They pierce the leaf or twig with their mouthparts and ingest a watery fluid from the xylem of the plant. Since they feed on a fluid, cicadas secrete a watery waste product. Yes, you can get pooped on by a cicada when walking under a tree!

Once the eggs are laid in a small cut on a tree, they hatch into little nymphs in about six weeks. Then they fall to the ground, where they burrow and spend years slowly feeding off the roots of trees and shrubs.

Even during large brood years, cicadas are not known for causing significant damage to trees, shrubs or crops. They will not decimate your garden and should not be sprayed with pesticides. And in the end, they are around only for about four weeks.

You may not realize the impacts that cicadas have on the ecosystem. When they emerge, especially in large numbers, they provide a bountiful feast for birds, reptiles and many small mammals. This in turn allows caterpillars and other small prey to have a reprieve and increase their numbers. Trillions of cicadas leave behind trillions of burrows in the ground. These can serve as homes for other creatures and are important in providing aeration to the soil. And last, in death cicadas add nutrients to the soil as they decompose (gross).

Cicadas are really cool!

Dr. Teich is the medical director for District Veterinary Hospitals in Navy Yard, Eastern Market and Brookland. Visit www.districtvet.com for more information.