Fireflies or lightning bugs are actually nocturnal beetles. There are about 2,000 firefly species that all have the same ability to glow because they have specific light organs, located under their abdomens. By combining oxygen and a substance called luciferin, fireflies can produce light without heat. Each firefly species has a unique blinking pattern to help attract potential mates. Their light can also serve as a defense mechanism, showing predators that they would taste bad.