Cicadas Are Awesome

Be aware that we are in line for another invasion, albeit an event we have experienced 17 years ago. Cicadas. Trillions of them.

Cicadas are stout-bodied insects with broad heads, clear-membraned wings, and prominent compound eyes. The species which inhabit the DC Metro Area are greenish in color and are about 2 inches long. Larval cicadas develop underground in burrows adjacent to tree roots, where they live for 2 to 17 years. Adults do not bite and do not eat leaves, but suck the sap from trees and shrubs, so unlike locusts, they usually do not cause significant damage to trees and plants.

There are in excess of 3,000 species of cicadas, sorted into two main categories: annual and periodical. The annual cicadas are present every year, while the periodicals spend most of their time underground, emerging once every decade or two. Every print / summer there are cicadas, but this particular May will be an inundation. Periodical cicadas are grouped according to their emergence pattern, with the groupings called broods. The Northeast is about to experience the emergence of Brood X, whose individuals have been slowly growing in their burrows for 17 years. There are other broods in our area, but X is by far the largest concentration.

When they emerge adult cicadas have one mission: breed. Female cicadas may deposit over 400 eggs on twigs and branches in trees, and these eggs in turn hatch into small nymphs in about 10 weeks. Falling from their perch, the nymphs burrow into the soil around the tree where they will mature over another 17 years. When that time comes and the soil temperature reaches 64 degrees, they emerge in mass, molt their shells, and begin the cycle once again. Adult cicadas don’t hang around too long – they have a life expectancy of four to six weeks.

Brood X will produce trillions of cicadas. Their sheer numbers may be a survival advantage: there are so many insects that it is impossible for predators to eat them all. Entomologists estimate that in some areas, the density of cicadas can reach 1.5 million per acre. To put this in perspective, the grounds of the White House could host over 27 million cicadas! Their molted shells, being light brown in color, can coat entire grassy areas.

What most people recall from 2004 was the sound produced by the Brood X males. They produce a clicking sound via vibrating membranes on their abdomen. Like singers in a choir, their calls are amplified by the sheer number of calling cicadas, with the resultant sound being akin to a car alarm, which can reach an incredible 100 decibels.

The spectacle of Brood X is more likely one of annoyance due to the copious numbers of shells and the drone of the mating calls, and less of danger. Cicadas themselves are not toxic. Some people even cook them. Birds find cicadas to be a high protein addition to their diet, along with small mammals and lizards.

Ingestion of a few cicadas by a dog will not cause any adverse affects – there is no need to panic if they are eaten. But ingestion of many cicadas may lead to upset stomach or potentially intestinal blockage as their outer shells are not readily digestible. If possible it is best to curb dogs from eating too many. Signs of over indulgence may include vomiting, diarrhea (possibly with blood), the inability to defecate, painful defecation, or general illness. Seek veterinary care as soon as possible if you have concerns.

Periodical cicadas are a marvel of our natural world. Although they may keep you awake at night, or provide your dog or cat a crunchy treat, recall that these insects spent 17 years underground awaiting this opportunity to emerge into the daylight – let them do their thing.

Dan Teich, DVM
Guy who appreciates bugs and Medical Director
District Veterinary Hospital