Beetles are insects mentioned briefly in the How to Train Your Dragon Book series.
Beetles include over 400,000 species, grouped in the Order Coleoptera. They are so numerous, that they account for about 25% of all known animals on the planet. Beetles are generally known for their particularly hard exoskeletons, and wing coverings - called the 'elytron'. Some are somewhat fantastical in shape like the Hercules beetle, while others may be known for their coloration, such as the red and black spots of the ladybug Family. Others are known for their bioluminescence - the fireflies.
Beetles have a wide range of habitat and diet, depending on the species. Some can live in freshwater, while other species live in arid deserts. Diet ranges from dung and detritus, to all manner of plant material to carrion, other insects, and even other beetles.
In the Book series, beetles are mentioned as metaphors or for describing something else.
In reality, beetles figure into many culture's myth and folklore. They are also both major pests and majorly beneficial to agriculture, depending on species. Beetles are also the most widely consumed type of insect, and can also be kept as pets.