Glowworms or fireflies are insects. They glow in the abdomen and belong to the group of beetles. That is why they are also called fireflies. Most of them can fly. Fireflies are found all over the world except in the Arctic. In Europe, glowworms are most likely to be seen in the summer, as that is the main time of the year when they are out and about.
There are fireflies that glow all the time and others that flash their lights. Firefly light can only be seen at night: not bright enough to see during the day.
The fireflies do not generate the light themselves. In their abdomen is a chamber with bacteria. These light up under certain conditions. So the fireflies are the home of the bacteria. You can switch the glow of the bacteria on and off again.
The fireflies use light to communicate with each other. Females use the glow to look for a male to mate with. Reproduction then proceeds as with all beetles: the female lays her eggs in groups. The larvae hatch from this. They later turn into fireflies.