Are fireflies going extinct? Why lightning bugs may soon flicker out.

For many people across the U.S., fireflies (or lightning bugs, depending on where you live) are one of the most cherished insects, with their beautiful flickering light displays on summer evenings.

More than 170 species of Lampyridae, or light-emitting beetles, light up North America's nights. Worldwide, there are more than 2,000 types – many that have been around for millions of years.

But some species are threatened with extinction.

Habitat loss, overuse of pesticides, climate change and increased light pollution threaten some fireflies. Yet, these hazards have varying effects on species depending on their genetics and environments.

Several firefly species are at risk, according to the Xerces Society and the International Union for Conservation of Nature Red List of threatened species. The IUCN looked at 128 species and determined 11% were threatened with extinction, and 2% are near threatened.

Fireflies are found all around the world, except for Antarctica. In the U.S., they prefer states that are warm and humid and are generally found east of the Rocky Mountains. According to the National Museum of Natural History, some species live farther west, but their glow is almost undetectable to the human eye.

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Fireflies produce light through a chemical reaction called bioluminescence in special cells in their abdomen. Oxygen combines with chemicals called luciferin and luciferase to generate light with almost no heat.

Scientists believe fireflies used their lights to ward off predators in the past, but they now use the flashing to find mates. Typically, males flash every five seconds and females every two seconds.

Fireflies go through a four-stage metamorphosis: egg, larva, pupa and adult. Their life cycle can be months or years. There are three main types of fireflies:

Contributing: Sarah Bowman, Indianapolis Star

SOURCE The Xerces Society; The IUCN Red List of Threatened Species; firefly.org; USA TODAY research