Yep, cicadas come out in "cycles". That's what lives in the ground of Catalpa
trees and the catalpa worms are great fishing bait, they say. They live there for years before they come out & don't live too long after they emerge & shed those shells. We used to call them locusts...I just found out the other day that they weren't, LOL.
Funny story, when my son was about 13 or 14 months old, he had just started walking, I saw one of the shells laying on our porch. So, I decided to show my little boy this cool shell. I called him over next to me, bent over to pick it up & it took off screaming, along with me & my son. Within seconds we were both crying, LOL! It's funny now, but it wasn't then!