Blowflies, commonly seen around homes and in natural environments, are a diverse group of insects belonging to the family Calliphoridae. These flies are widespread across nearly every continent, familiar due to their distinct appearance and noisy flight. Often associated with decaying organic matter, blowflies play various roles in the environment and interact with humans in various ways.
Identifying Blowflies
Adult blowflies measure between 1/8 and 5/8 of an inch (3 to 16 mm) in length, making them slightly larger than the common housefly. They have striking metallic coloration, including shades of blue, green, black, bronze, or copper. Many species possess bristly bodies and prominent reddish-brown eyes, with transparent wings held flat over their backs when at rest.
They are often found near decaying organic material like animal carcasses, garbage, or waste, attracted by scent. Their larvae, often called maggots, are pale yellow to white, worm-like, and lack legs and eyes. Their tapered head features hook-like mouthparts used for feeding.
Life Cycle and Habits
Blowflies undergo complete metamorphosis, progressing through four distinct stages: egg, larva, pupa, and adult. Adult female blowflies lay their eggs, in batches of 100 to 200, directly on decaying organic matter, including carrion, feces, or open wounds. A single female can lay up to 2,300 eggs during her lifetime.
Eggs hatch rapidly, within 12 to 48 hours, into cream-colored larvae (maggots). Maggots are voracious feeders, consuming decaying tissue and growing quickly through three larval stages (instars) over about one week. After feeding, mature maggots migrate from their food source to a dry, secluded location, often in soil, where they transform into pupae within a hardened case called a puparium.
The pupal stage lasts from several days to two weeks, depending on temperature. Once developed, the adult blowfly emerges from the puparium, ready to mate and continue the cycle. The entire life cycle, from egg to adult, spans two to three weeks, though this varies with temperature.
Their Impact on Ecosystems and Humans
Blowflies play a significant role in ecosystems as primary decomposers. Their larvae efficiently break down organic waste, such as dead animals, by consuming decaying tissues. This process recycles nutrients back into the environment, contributing to natural system health.
Their predictable life cycle makes blowflies invaluable in forensic investigations, particularly for estimating the post-mortem interval (PMI), or time of death. Blowflies are often among the first insects to arrive at a deceased body, sometimes within minutes, to lay eggs. By studying the developmental stage of larvae and considering temperature, forensic entomologists can determine how long a body has been deceased.
Blowflies also have medical and nuisance impacts on humans and animals. Their larvae can infest the living tissues and open wounds of animals and, occasionally, humans, a condition known as myiasis.
Adult blowflies are also mechanical vectors of pathogens. They pick up bacteria from unsanitary environments like feces and decaying matter, transferring contaminants to human food and surfaces. These can include bacteria responsible for conditions such as Helicobacter pylori, dysentery, salmonella, cholera, plague, anthrax, and tuberculosis. Their attraction to garbage and waste also makes them a common nuisance around homes and agricultural settings.