The glow worm is a medium to large sized invertebrate that is famous for having a green and yellow coloured light on the end of it's tail. Glow worms are found inhabiting dense woodland and caves around the world with the exception of the Americas and glow worms are one of the few insects that are found inside the colder Arctic Circle. Glow worms are nocturnal animals which means that they are active during the dark night which is when their glowing rears can be seen.