You could call it biological fireworks — summer fireflies are still lighting up the night in Iowa fields and gardens.

“Watching fireflies is one of the real treats of living here in the Midwest,” Iowa State University entomologist Donald Lewis says. Lewis calls their bio-luminescence a “living light show” and he says it’s a great spectacle to enjoy.

The population of lightning bugs generally peaks in Iowa in the middle of July. There are a couple dozen species of fireflies in the United States and there are hundreds around the world. There’s only a small selection in Iowa though Lewis says their numbers are large and they “give us a pretty good show.”

The bug specialist says their “cool” light is created by a combination of two chemicals. There’s a protein called luciferin and an enzyme called luciferase. When those two chemicals are mixed in the presence of oxygen in the tail of the firefly, the chemical reaction produces a result that’s nearly 100 percent light.

Lewis says all the methods human have invented to generate light also produce heat and scientists for years have studied fireflies to see how they create light without the unwanted thermal side effects.