Blow flies, also known as bottle flies, are a common group of insects recognized by their metallic bodies. Slightly larger than typical house flies, they are known for their noisy flight. These flies are widely associated with decay and are found globally. They play a role in nature as decomposers, often among the first insects to arrive at decaying organic matter.
Life Cycle and Breeding Grounds
Blow flies undergo a complete metamorphosis, progressing through four distinct stages: egg, larva, pupa, and adult. The adult female initiates the life cycle by laying eggs directly onto decaying organic material, which serves as the primary food source for the developing larvae. These breeding grounds typically include animal carcasses, animal waste, rotting food, or even open wounds on living animals. A female blow fly can lay hundreds of eggs per batch, and some species lay thousands over their lifetime.
Eggs are small and white, and hatch into larvae within 24 to 48 hours. These larvae, commonly known as maggots, are eyeless and legless, feeding voraciously on the decaying material. They develop through three larval stages. After several days of feeding, the mature maggots leave their food source and seek a drier, protected location, often in the surrounding soil, to pupate.
During the pupal stage, the maggots transform inside a tough cocoon. This stage can last for about eight days, after which the adult blow fly emerges. The entire life cycle, from egg to adult, typically takes between two to three weeks to complete. Adult blow flies generally live for two weeks to a month.
Attraction and Entry Points
Adult blow flies are highly attracted to the odors emitted by decaying organic materials. Their acute sense of smell allows them to detect these scents from significant distances. Common attractants include dead animals, uncovered garbage, pet waste, compost piles, and even fermenting fruits or spilled animal feed. The presence of blow flies indoors often indicates a nearby source of decaying material, such as a dead animal or forgotten food.
These flies can gain entry into homes and other structures through various openings. Open windows and doors are common access points if not equipped with intact screens. Small cracks in foundations, gaps around pipes, and unscreened vents also serve as potential entryways. Damaged weatherstripping around doors or gaps in door sweeps can also allow them to slip inside. Occasionally, blow flies may even hitchhike indoors on people or pets.
Controlling Their Presence
Preventing blow flies involves a multi-pronged approach that focuses on sanitation and exclusion. Regularly disposing of waste and ensuring all garbage cans have tight-fitting lids is an effective deterrent. Cleaning trash receptacles frequently helps eliminate residual odors that attract flies. Promptly cleaning up pet waste from yards also removes a significant breeding ground.
Exclusion methods aim to block their entry into buildings. Inspecting and repairing screens is important to prevent flies from flying indoors. Sealing cracks and gaps in structures and around utility entry points can close off hidden access routes. Maintaining proper door sweeps and ensuring doors fit tightly within their frames further limits entry. Reducing outdoor attractants, such as promptly removing any dead animals from the property, also lessens the likelihood of flies congregating near the home.