Bottle Fly

The bottle fly, most often referring to the blue bottle fly, belongs to the family Calliphoridae, commonly known as the blow flies. This large family of true flies is distributed worldwide and is easily recognized by the metallic sheen shared by most of its members.

Bottle flies play an important role as decomposers, being among the first insects to locate and colonize decaying organic material, which speeds up the breakdown of dead plant and animal matter in the environment. Their conspicuous coloring and loud flight make them one of the most familiar large flies encountered outdoors.

• Robust, thick-bodied fly, 10–14 mm long, roughly twice the size of a common house fly.
• Body covered in a shiny, metallic blue or blue-black sheen that catches the light.
• Large red compound eyes and short, bristly black antennae.
• Single pair of clear, veined wings; strong, loud, low-pitched buzzing flight.
• Lookalike: the closely related green bottle fly looks nearly identical but has a metallic emerald-green body instead of blue.

Found nearly worldwide in temperate and subtropical climates, especially in urban, suburban, and agricultural settings. Adults are active from spring through fall and are frequently seen around garbage areas, compost, outdoor food, and gardens, often basking on sunlit surfaces.

Adults feed on nectar, decaying organic matter, and sugary substances, using their sponging mouthparts to lap up liquids. Females are strongly attracted to carrion and other decomposing material, where they lay eggs so larvae can feed and develop. As decomposers, bottle flies help recycle nutrients back into the ecosystem and serve as a food source for birds, spiders, and other predators.

Bottle flies undergo complete metamorphosis. Females lay batches of eggs on decaying organic matter, which hatch within a day into legless maggots that feed and grow rapidly through several molts. Pupation occurs in a hardened brown case in nearby soil, and adults emerge within one to two weeks under warm conditions; multiple generations occur per year in warmer climates.