Lightning bugs!

The first time I saw one of these was when I was waiting for 4th of July fireworks when I was 12 years old. I thought they were some of the coolest bugs ever.  Apparently my grandmother did as well, but for other reasons - when she was little, she mashed them up on her hands and pretended she was wearing sparkling diamond rings. Now, I can't say I did that myself, but I DID very much wonder what made these insects glow the way that they do.

First of all, what is this insect? It's actually a member of the order Coleoptera, so it is actually a type of beetle. In the daytime, they look like this:

http://en.wikipedia.org/wiki/File:Photuris_lucicrescens.jpg

But you're probably more familiar with the cool green glow that you see blinking on and off at night.

http://en.wikipedia.org/wiki/File:Firefly_composite.jpg

So what is that, exactly? Bioluminescence, that's what! You may have heard of this before - there are quite a few members of marine life that have this chemical reaction as well. Some squids, crustaceans, fungi, and fishes are bioluminescent - usually those in the deep waters that don't have much access to sunlight.

http://en.wikipedia.org/wiki/File:PanellusStipticusAug12_2009.jpg

Bioluminescent dinoflagellates are also responsible for the green glow that oceans occasionally appear to have. Bioluminescence is a chemical reaction involving an enzyme called luciferase, according to my handy Borror and Delong's Study of Insects (2005) Entomology text. When the insect breathes in air, it is oxidized, and then the energy is released as light. This light can be seen in the abdomen of a lightning bug.

Most likely, the point of this glow for lightning bugs is to attract mates, although sometimes it is used in a predatory fashion to attract meals. Females also tend to have a brighter glow than males.

Keep your eyes open and maybe you'll see these neat little beetles while you're waiting for your fireworks show. Happy 4th, everyone!