Cycling Cicadas

For all of the high-tech science that cicadas are providing the researchers at North Carolina Central University’s Biomanufacturing Research Institute and Technology Enterprise (BRITE), it seems only fitting to talk a little more about the mysterious insects. That’s because there might not be another insect that provokes more emotional reaction than the periodical cicada; a creature that you will only find between the eastern half of the Great Plains and the Atlantic Coast.

That’s right.

Periodical cicadas are not found anywhere else on Earth.

There are six species of the Magicidada, the name scientists have given the periodical cicada. The unique insects emerge in different places in different years. About half of the species crawl out of the ground in 17-year cycles in the Midwest and Northern states, while the remainder pop out every 13 years in the Midwest and South. Scientists don’t know what triggers the cicadas to emerge from their sleep.

Each group in a unique territory is called a brood. There are roughly 17-20 broods. Each brood is still on either the 17 or 20-year cycle, it’s just that the cycles occur at different times.

Cicadas appear in huge numbers, which can top 100 or more insects per square yard. The numbers are so dense it can appear as if trees and even lawn furniture are alive if they are covered with the bugs. Scientists believe the cicadas synchronize to appear in such large numbers to help with their survival. The hypothesis is that birds and animals eat so many insects when the brood first emerges that they are too full to continue eating. The rest of the brood is then free to reproduce.

Reproduction is the primary goal for cicadas. Not long after crawling out of the ground, cicadas molt out of their crusty shells. Within hours, they grow dark new shells over their pale white bodies and then begin flying from tree to tree. The cicadas’ song is all up to the guys. Male cicadas create songs by vibrating rigid abdominal membranes and amplifying the sound with their hollow bodies. Males bond together in packs and seduce females to sunlit treetops to mate. Apparently it’s the song, and not the orange eyes, that melt a female cicada's heart.

Females can mate several times in an adult life. Those lives last about three weeks. Once the cicadas get busy, the females fly to a nearby branch, gouge a notch in the branch and lay about 20 eggs inside. The process continues until all of the eggs are laid.

The guys, once finished, die. They live for about one week.

In about six weeks the tiny cicadas, which are about the size of an ant, emerge from the tree branch notch and tunnel underground. There, the cicadas will feed on the juices of plant roots until it is time to fly again.

— Frank Graff

Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!

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