Starting this week and lasting into June, billions and possibly even trillions of cicadas will emerge across much of the eastern half of the United States.

The thumb-sized insects are harmless, but they are large, noisy and clumsy. They climb out of their underground homes en masse after 17 years of slow development with only one goal in mind - finding a mate.

The last time this happened at such a scale was in 1987, and Baker was working in the emergency room of Cincinnati Children's.

"We just noticed when this all started, children were coming in and having injuries related to cicadas," Baker said in a telephone interview.

"After the third or fourth one we decided to keep a list."

They noted 12 injuries that were fairly significant, Baker said. He wrote a letter to the journal Pediatrics afterward, outlining the cases.

"They were all related to kids trying to get away from what they perceived as cicadas flying at them, or the children were trying to kill them," Baker said.

"They do freak people out. They are big. They are bigger than most other flying things and they really don't seem to have any tremendous purpose in which direction they are flying."

Several children fell off bikes, Baker said. "We had a concussion, a 9-year-old who was fleeing a cicada on her bicycle and fell off," he said.

Another child hit his head on a brick wall while he was running away from one of the insects.

"We had a stab wound to the arm from a kid who was trying to kill a cicada on the arm of another child but unfortunately he was using a knife," Baker added.

"Another kid tried to kick one under a lawn mower and cut his foot, and we saw a crush injury to the hand when a kid tried to put a cicada under the wheels of a moving car."

All parents can do is try and supervise their children and remind them that that the cicadas are harmless, Baker advised.

"There's a lot on the news, but I think that just gets kids kind of excited," he said. "Kids don't always do what they are told."