No summer evening is complete without watching—and sometimes catching—fireflies. There are about 2000 different species of lightning bugs, and there's still a lot that scientists don't know about them. Here are a few things we do know.

1. They’re actually not flies—they’re beetles.

Courtesy of Flickr user Wesley Fleming

Up close, it's easier to see that fireflies are beetles. And like all other beetles, they have hardened forewings. Fireflies use the forewings—also called elytra—for balance while in flight.

2. A firefly's glow is a chemical reaction—which makes them bioluminescent.

According to LiveScience, the light is produced when oxygen is mixed with a pigment called luciferin, an enzyme called luciferase, and a chemical that provides cells with energy called adenosine triphosphate. The final part of the formula is uric acid crystals, which are located in the cells that make the light and shine the light away from the firefly's body. (The light-emitting part of the firefly is called a photic organ, by the way.)

3. Males focus on finding a mate.

At the nucleus of their night flights, the brightness of their glow, and their flashing patterns is one thing: reproduction. These guys are intent on mating. Typically, the females sit immobile, and only flash back when they see a male with a particularly impressive display.

4. Each species has its own flash pattern.

As males fly through the air searching for a mate, each uses a "flash fingerprint" specific to its species. According to the American Museum of Natural History,

Males fly through the air and search for females with a species-specific light display. Some flash only once. Some emit “flash trains” of up to nine carefully timed pulses. Others fly in specific aerial patterns, briefly dipping before sharply ascending and forming a “J” of light. A few even shake their abdomens from side to side and appear to be twinkling.

Scientists can use these patterns to determine how many species are in an area.

5. Some sync up.

Called "simultaneous bioluminescence" by scientists, the phenomenon of fireflies flashing in unison only happens in two places in the world: southeast Asia and the Great Smoky Mountains National Park in Tennessee.

6. Flashing fireflies almost don’t exist west of the Rocky Mountains.

There are a few rare exceptions, but for the most part, flashing fireflies don't live west of the Rockies. Why? Well, no one is really sure. Whereas flashing fireflies communicate with their flickers, non-flashing ones use phermones to stay in touch with one another.

7. They can be poisonous.

Not only do fireflies taste nasty, they can actually kill. When predators attack, fireflies kick in to a process called "reflex bleeding." They shed drops of blood that contain bitter-tasting chemicals that are poisonous to vertebrates, including lizards and sometimes birds. They're not so great for humans, either: When scientist Marc Branham with the American Museum of Natural History gently put a firefly he'd caught in a net between his lips (his hands were full with a jar), “Both lips went numb. Then my throat constricted. They really taste sort of astringent. I quickly put them into my jar and I haven’t done that since.”

8. In much of Europe, female fireflies don’t actually fly.

European female fireflies remain flightless into adulthood and take on the form of a worm that glows rather than flashes.

9. Female fireflies can be cannibalistic.

In general, fireflies don't feed, but when they do, they tend to eat mites or pollen. However, the femme fatales of the genus Photuris like the taste of their own. Using "aggressive mimicry," the female of this particular subfamily waits for a male firefly to flash, then imitates that male's flash pattern, suggesting that she is a receptive mate. After luring him in, she chows down.

10. And the larvae aren't a picnic, either.

These glowing worms will follow the slime trails of snails and slugs, paralyze them with a bite, and chow down.

Sources: National Geographic, About, Firefly, LiveScience, and American Museum of Natural History ( target="_blank">2), Animal New York