Ending a Report: How Fireflies Glow

Little Lights of Summer

1On warm summer nights, tiny lights blink on and off above lawns, fields, and the edges of woods. These lights come from fireflies, which many people call lightning bugs. Despite their name, fireflies are not really flies. They are beetles, and they have an amazing ability: they can make their own light. In this report, I will explain how fireflies make their light and the ways their glow helps them survive.

2A firefly makes its light inside its own body. Near the end of its abdomen, which is the back part of an insect's body, a firefly has special light organs. Inside these organs, chemicals mix with oxygen, and that mixture gives off a glow. Scientists call light made by a living thing bioluminescence. Many light bulbs become hot after they have been on for a while, but a firefly's light gives off almost no heat. For this reason, people often call it "cold light."

3Fireflies use their light mostly to send messages to each other. In many kinds of fireflies, the males fly through the air and flash a pattern of light. The females wait in the grass or on low plants and flash back an answer. Many kinds of fireflies have their own special pattern. Some blink quickly several times in a row, while others make one longer, slower glow. By watching for the right pattern, a firefly can find a partner of its own kind, even on a very dark night.

4The glow may also help protect fireflies. Their bodies contain chemicals that taste bad to many animals that hunt insects. Scientists think the light may work like a warning sign that tells hungry animals, "Do not eat me!" An animal that bites one bad-tasting firefly may learn to stay away from the glowing insects it sees later. Even young fireflies, called larvae, can glow, and their light may send the same warning. Because they glow, the larvae are sometimes called glowworms.