LOUISVILLE, Ky. — Thousands of cicadas are singing in Kentucky this summer.

Brood XIV, also known as the bourbon brood, is coming out for the first time in nearly two decades. One of the largest broods of periodical cicadas, they come out once every 17 years. 

“This is a big year because we have an emergence of the 17-year cicada," said Steve Yanoviak, University of Louisville professor and insectologist. "This is not something that happens every year, obviously."

Yanoviak, who has had a lifelong passion of studying insects, said he often gets several questions about cicadas this time of year, especially their shells that they leave behind. Little shells of cicadas cover trees, fences and sidewalks all over Kentucky.  

“What you see here is the exoskeleton, the outside skin of the immature, the juvenile insect that lived in the ground for 17 years," Yanoviak said. "Now, they don't have wings when they live in the ground, but they want to have wings as adults so they can find other adults to mate with."

"This insect crawled out of the ground, crawled up this tree, shed its skin and out emerged some wings during that process. Now you have the adult form of the insect." 

Although they might be noisy, he said they don’t harm people and cicadas are important to the ecosystem.

“They actually serve a lot of important ecological functions," Yanoviak said. "Anything that comes out in this huge amount of numbers at one time provides a lot of food for things like birds and bats and other species that are out there feeding on insects. They also, during their activities underground for 17 years, are aerating the soil, so they're providing opportunities for roots to grow through the soil."

Brood XIV will be out until early July. Afterward, Kentucky's annual cicadas will be out until as late as September.