The 17-Year Cicadas Will be Back!

May 27, 2020 By Ritali J, Writer
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Cicada in the grassWith all that 2020 has brought, it should be no surprise that we have another rare event coming our way.

This year, the 17-year cicadas will emerge in great numbers, possibly trillions!

There may be almost 1.5 million cicadas per acre of land in the areas they will emerge in, including Southwest Virginia, North Carolina, and West Virginia, between the end of May and beginning of June. 

Cicadas that emerge in similar patterns with an identical life cycle are classified into broods. There are 15 different broods for 17-year cicadas, and this year, Brood IX will be present.

Are Cicadas Dangerous or Harmful?

Cicada on tree trunkPeriodical cicadas are large insects, 1.5 inches (3.8 cm) in length, with clear-wings and a reddish-orange color. They don’t bite or sting, so they aren’t dangerous to humans.

Visitors from China, Japan, Asia, and Europe actually look forward to the cicada emergence, since the rare event is seen as good luck in different cultures. However, cicadas can be disturbances when they emerge because of the extreme noise they create to mate. The sounds can be heard four to six weeks after emergence.

Cicadas also damage orchids, vines, and especially trees when females lay eggs. They create slits in tree branches to lay and secure their eggs. As a result, the branches weaken, turn brown, and wither away. Cicada swarms are huge because even though they only live two to four weeks as adults, females leave behind hundreds of eggs.

What is the Life Cycle of a 17-Year Cicada?

Did you know that cicadas have the longest life span of all insects in North America? They live only a few weeks in adulthood but seventeen years of childhood!

Young cicadas spend 17 years underground, living a few inches (5-6 cm) beneath the soil. During this time, they eat tree roots and dig tunnels for nutrients. Xylem is a fluid tissue that transports water and minerals in plants and tree roots. It may have a property that helps young cicadas know when 17 years have passed based on annual tree cycles. 

The fall before the cicadas are to emerge, they move into a nymph stage, which is like a teenager stage for insects. During the nymph phase, the insect looks similar to the adult version, just without wings, but it still has to slowly transform to become an adult and form its wings.

In the soil, the nymphs build mud tubes, also known as cicada huts, to emerge, ideally when the soil temperature is 64℉ (17.78℃). Then, one night, millions of cicada nymphs rise through their holes and molt their skins in under 60 minutes! 

The nymphal cicadas are now adults, with soft exoskeletons ready to harden and their very own wings. At this point in the cicada’s lives, its sole purpose is to mate and lay eggs before it dies.

You might wonder why the life cycle of a cicada is so strange. Scientists believe that the cycle evolved to help the cicada population survive since their predators won’t be solely dependent on them for food. The science and evolution behind this rare event is so interesting, we might as well enjoy it!

Sources: CNN, Accuweather, HowStuffWorks, BBS, Thought Co.