��������

Throughout the spring and early summer, trillions of cicadas will emerge from over a decade underground to complete their life cycles. For several weeks, they’ll test out above-ground skills they’ve never before employed – flying, singing and mating their way to continued survival.

Try to imagine clawing through the darkness into that first ray of sunshine, unfurling your wings and drunkenly weaving your way into the treetops, where you erupt into song with thousands of your kind. Of course, we don’t know how the cicadas actually experience this phase of their lives, but Professor Chris Paradise says cicadas have captured the human imagination for thousands of years.

“In various cultures, cicadas represent or symbolize resurrection, immortality, personal change, renewal, rebirth, spiritual realization and transformation. Individuals may use cicadas in art, poetry or tattoos, as symbols to represent personal transformation,” he said. “The cicada starts as an underground, or earthbound, nymph, and emerges to become a beautiful adult, complete with wings and a song, and that imagery has meaning to many people.”

Because of their song and the season in which they emerge, cicadas also have become symbols for musicians or singers, as well as symbols of the upcoming harvest.

We checked in with Paradise, a professor of biology and chair of environmental studies, to learn more about these long-awaited visitors. 

Why is this cicada event significant? 

Many insects are adapted to emerge synchronously to maximize reproductive opportunities and seasonal availability of resources. In the case of cicadas, they can emerge in such great numbers that it’s been hypothesized to be a mechanism to swamp predators (known as predator satiation). Even when predators gorge themselves on the abundant and juicy cicadas, many cicadas will escape and survive to reproduce. Those great numbers make the event noteworthy – if you live in an area where an emergence is happening, you will definitely notice it! The sound can be deafening, but it only lasts for a few weeks. It’s an event highly anticipated by many people who are fascinated by cicadas, and not just among the entomology crowd. It is a biologically significant event that we can predict based on decades of observation, and the numbers that emerge may tell us something about how cicada populations are faring during this time of the so-called insect apocalypse, where significant declines in insect abundances have been documented worldwide. 

Describe the cicada life cycle, the process of emergence and what happens when they reach above ground. 

The species that could emerge around Mecklenburg County are known as 13-year cicadas, which are several closely related species that all live underground as nymphs for 13 years before emerging aboveground for a few brief weeks in the late spring or early summer. I say “could” because their appearance will be spotty. A friend sent me a picture of a cicada that emerged in south Charlotte, but they may not show up in ��������. 

During that brief adult stage, males call for females, in some species females will call back, and once they find (amidst all the noise) and accept one another, they mate. The female lays eggs in twigs up in the trees using a very stout ovipositor, which allows them to insert eggs under the bark. The eggs hatch a few weeks later and the nymphs drop down from the tree and burrow underground. They then use their stout proboscis to attach themselves to tree roots and live a long quiet nymphal life until it’s time to emerge from underground, crawl up on a tree, fence post, or whatever vertical surface they can clamp onto and metamorphose into the adult – unlike many other insects, they do not have a pupal stage, so go directly from nymph to adult. 

Cicadas, and likely many other insect species, pump hemolymph (their version of blood) into the wings as they unfold during emergence, but then after the wing has fully expanded and hardened, they pump it back out to produce a strong yet lightweight wing. Once their exoskeleton has hardened, the males fly up higher in the trees and start singing.

How might the cicada event affect life for people in areas where broods emerge?

Well, there will be noise, and I know some people who will actually vacate the area while the cicada mating is happening. But we hear it every summer, just not these species and not with this intensity. In areas with high densities, the cicadas will likely be flying about some, although much of the time the males will stay in trees calling for females. 

Some people might be frightened by large insects flying about, but cicadas do not bite or sting. Aside from occasionally landing on someone or bumping into them, they are harmless. Even the latter is pretty rare – they look like ungainly fliers, but they are pretty good at avoiding large objects such as humans. 

How do they make the sound we hear? 

Male cicadas have tymbals, which are membranes on the underside of the abdomen that vibrate very quickly when pulled on by connected muscles. The vibrations are what create the cicada’s songs, and enlarged cavities behind the tymbals that are part of the respiratory system act as amplifiers of the song. This is one way you can tell males from females – if you pick one up and look at the underside, look for a pair of membranous circles, almost like tiny little drumheads.

Cicadas have different calls, including mating calls to attract females, territorial calls, courting calls once a female responds, and alarm or distress calls, which might be used if your dog tries to eat a live cicada! If you are lucky enough to be in an area where there is a mass emergence, you might even hear a synchronization of mating calls by a large group of males, which they do to attract females to their location. I mentioned earlier that females can respond to males with their own calls. Females do not have tymbals, but they can flick their wings and make stridulations, sort of like how crickets produce their calls.

Do they affect plants or other animals (what happens if my dog ingests one)? 

Cicadas can damage trees during the egg-laying process. The slits made by females in small branches to lay eggs can severely weaken them. Weakened branches can snap off in the wind and when a high density of females lay eggs on the same branches, those branch tips may die. This can be especially injurious to saplings, especially the oak, maple, fruit trees, and redbud on which they prefer to lay eggs. The larvae are herbivores and feed on tree roots, but I've not heard of cicadas harming trees that way. If enough of them are feeding on the same tree, they could slow growth, but it would likely be difficult to measure the effect. Also, because they grow so slowly, they would not be rapidly depleting the fluids of a tree, but again it likely depends on their abundance on a tree’s roots.

A lot of dogs like to catch them and sometimes eat them. The American Kennel Club states that most dogs have few issues eating a few cicadas, but if your dog consumes many of them, they may get quite sick. Exoskeletons are difficult to digest, and that can cause upset stomachs and abdominal pain. In extreme cases, vomiting and bloody diarrhea may result, even requiring medical intervention.

How can families make this a teachable moment for children? 

The way that we react to cicadas, or any insect for that matter, is observed by children and sets an example. Studies have found that parents who fear insects are likely to pass that behavior on to their children. After learning about their life cycle above, parents can teach kids about insect life cycles or about why some species become adults all at the same time. When the adults begin to die, they will often be found on roads and sidewalks – parents can pick up a cicada and teach their children how to look for the tymbals or the ovipositors to determine whether that individual was a male or a female.

Anything else you’d like to share?

In some cultures and countries, a periodical cicada emergence is a time to collect a culinary delicacy, as many other cultures regularly consume insects as part of their diet. In fact, there are websites dedicated to offering up cicada recipes. However, two cautionary notes: 1) do NOT eat insects if you have a shellfish allergy, and 2) always cook insects before eating. 

Explore Biology at ��������

Explore Environmental Studies at ��������

Additional Coverage

On Course: Insect Essentials for a Bug-Phobic World