This question crops up from time to time, especially among those of us who have fond childhood memories of chasing these amazing creatures on summer evenings, capturing them in glass jars to watch the pulsating glow, then releasing them to the night. The pulsating glow is a mating signal. The greenish-yellow area on their undersides glows, thanks to a chemical reaction in the abdomen. This is a cool light rather than one that produces heat. I've read that a lightning bug is only able to glow 3 to 8 weeks of its life.
Female beetles lay eggs in damp areas with low vegetation.
The eggs hatch and the larvae emerge, feed and then go underground for winter. The larvae, which also give off a faint light, are known as glowworms. They are beneficial in that they inject a paralyzing fluid into aphids, slugs and snails, then eat these pests. The larvae pupate in spring, and adult lightning bugs emerge in early summer. No, leave the foliage, then lift the corms when the leaves have yellowed in the fall and store them in a dry, well-ventilated space until planting time next year.