Otherwise known as lightning bugs or fireflies, these glowing insects can vary in size drastically by species. The males are luminescent while the females are not, but some entire species cannot glow at all. Those that are nocturnal have males that can emit light; however, diurnal species don’t need this skill and therefore do not have it. Larvae feed on other larvae, snails, and slugs while adults have a very diverse diet, and some do not even have mouths at all.