Bottle Flies, commonly known as **blow flies**, belong primarily to the family Calliphoridae. They are easily recognized by their metallic blue, green, or black bodies, often resembling large house flies. Bottle flies are medically and economically important because the adult flies can transfer pathogens from unsanitary breeding sites to human food, and their larvae (maggots) are significant in forensic science and can sometimes cause myiasis (infestation of living tissue) in animals.
Taxonomy and Classification
Bottle Flies are members of the family Calliphoridae in the order Diptera (true flies). Common genera include *Calliphora* (bluebottle flies) and *Lucilia* (greenbottle flies). They undergo complete metamorphosis (egg, larva/maggot, pupa, adult). Their life cycle is often extremely fast, which is a key factor in their role in forensic entomology and disease transmission.
Physical Description
Adult Bottle Flies are typically 6–12 millimeters long and have robust, hairy bodies. They are characterized by their brilliant, iridescent, metallic coloring—most often blue, green, or copper—which gives them their common names. They possess large, reddish-brown compound eyes and are strong, rapid flyers, making a loud buzzing sound.
The larvae, or maggots, are creamy white, legless, and conical, tapering towards the head. They are specialized feeders on decaying organic matter and can reach 10–20 millimeters in length before pupating.
Distribution and Habitat
Bottle Flies are cosmopolitan, found globally wherever decaying organic matter is available. Their habitats are generally unsanitary and include garbage bins, manure piles, compost heaps, slaughterhouses, and decomposing animal carcasses. They are attracted to structures by the odors of these materials, and often enter homes in search of food or to lay eggs on exposed garbage or spoiled meat.
The presence of a large number of bottle flies indoors often indicates a decaying animal carcass (e.g., a dead rodent or bird) hidden within a wall void, attic, or chimney.
Behavior and Life Cycle
Bottle Flies have one of the fastest development rates of any insect, sometimes completing their life cycle in as little as 10 days in warm weather. Females lay masses of up to several hundred eggs on decaying protein sources. Maggots hatch rapidly and feed ravenously, passing through three larval instars.
Once feeding is complete, the maggots crawl away from the food source to a dry, protected site (often in the soil or under debris) to pupate in a dark, reddish-brown puparium. The adult then emerges and immediately begins seeking food and mates.
Feeding and Health Concerns
Adult flies feed on sugary substances, nectar, and the liquid products of decay. However, because they alternate between highly contaminated sites (feces, carrion) and human food sources, they are effective **mechanical vectors** for disease agents such as bacteria that cause dysentery, food poisoning, and cholera. The adults carry these pathogens on their feet, mouthparts, and bodies.
In veterinary science, the maggots of some species cause **myiasis**—infestation of wounds or natural body cavities in livestock and sometimes pets. In forensic science, the stage of development of the maggots on a corpse is a crucial indicator for estimating the **postmortem interval** (time since death).
Management and Prevention
Management is based on **sanitation and exclusion**. The primary control measure is the prompt and proper disposal of all dead animals and garbage. Garbage bins should be kept tightly sealed and cleaned frequently. Doors and windows should be properly screened to exclude adults from indoor environments.
If an indoor infestation occurs, the source (e.g., a hidden carcass) must be found and removed. Adult fly control involves space sprays (aerosols) and residual insecticides applied to common resting surfaces, but this is always secondary to eliminating the breeding site.
Conservation and Research
Bottle Flies are generally not conserved. Research is largely focused on their importance in forensic entomology to improve methods for crime scene investigation, and on public health, studying their role in the transmission of antibiotic-resistant bacteria from decaying matter to food.