A bluebottle is a type of large fly with a shiny, metallic blue or green body that looks almost jewel-like in sunlight. These flies are common around the world and get their name from their distinctive coloring, which can shimmer like a blue glass bottle. You've probably heard their loud, buzzing flight and seen them bumping against windows trying to get outside.

Bluebottles are attracted to garbage, rotting food, and dead animals, where they lay their eggs. While this makes them seem gross, they actually play an important role in nature by helping to break down and recycle dead matter.

The word can also refer to the Portuguese man o' war, a sea creature that looks a bit like a jellyfish and has a bright blue, gas-filled float that resembles a bottle bobbing on the ocean surface. These marine bluebottles have long, stinging tentacles and are found in warm ocean waters. In Australia, people often call them bluebottles and watch for them at the beach, since their sting is quite painful.