Most people seeking information about the buzzing, metallic insects frequently encountered in homes and around garbage are referring to a specific group known as blow flies. These are true flies belonging to the Order Diptera, and they play a significant, though sometimes unwelcome, role in the natural world. This article focuses on the Green Bottle Fly, the most common insect associated with this description, while also clarifying the identity of other insects mistakenly grouped under this name.
Identifying the True Green Flies
The Green Bottle Fly primarily belongs to the genus Lucilia, with Lucilia sericata being the most recognized species worldwide. These flies are easily distinguishable by their brilliant, iridescent coloration, which ranges from a dazzling metallic green to a blue-green or even golden sheen. The adult insect is medium-sized, typically measuring between 10 to 14 millimeters in length.
The Green Bottle Fly is attracted to decaying organic matter as it seeks out sources of protein for its offspring. They are strongly drawn to garbage, feces, and, most notably, carrion, which serves as the primary breeding site for their larvae.
Life Cycle and Ecological Role
The life cycle of the Green Bottle Fly begins when a female deposits egg masses, often hundreds at a time, directly onto a suitable food source like a carcass or decaying meat. Development time is highly dependent on ambient temperature, with eggs hatching into larvae, commonly called maggots, in as little as nine hours in warm conditions.
The larva passes through three instars, feeding voraciously on the dead tissue for three to ten days before crawling away to find a protected location for pupation. This rapid development makes the Green Bottle Fly useful in forensic entomology, where the maggot’s developmental stage can estimate the time of death. Larvae also have a medical application in maggot debridement therapy, consuming necrotic tissue from wounds without damaging healthy flesh.
Adult flies serve an ecological function as decomposers, helping to break down organic waste and recycle nutrients back into the ecosystem. The adults feed opportunistically on various substances, including feces, carrion, and even flower nectar, contributing to the pollination of certain plants.
Confusing “Green Flies” with Other Pests
The term “green fly” is frequently misapplied to the Green Aphid, a small, soft-bodied plant pest belonging to the Order Hemiptera, not Diptera. Aphids, such as the Green Peach Aphid (Myzus persicae), are tiny, usually less than 3 millimeters long, and primarily green, yellowish, or sometimes pink.
Unlike the flies that seek decay, aphids feed exclusively on the sap of living plants, using piercing-sucking mouthparts to draw nutrients from stems and leaves. They are often found clustered in dense colonies on new growth and can be wingless or develop wings when overcrowding triggers migration to a new host plant. Another green insect sometimes mistaken for a fly is the Green Lacewing, a beneficial predator whose delicate, net-veined wings and golden eyes distinguish it.
How to Manage Green Fly Presence
The most effective method for managing Green Bottle Flies involves a proactive focus on sanitation and exclusion, as they are primarily attracted to breeding sites. The first step is the immediate removal of all sources of decaying organic material, including pet waste, dead rodents, or uncovered food scraps. Garbage cans should be cleaned regularly and must be fitted with tightly sealed, secure lids to prevent access.
Physical barriers are highly effective for preventing adults from entering a structure, so all window and door screens should be maintained without holes or tears. Gaps, cracks, or crevices around utility lines, doors, and windows should be sealed with caulk or weather-stripping. For immediate control of adult flies, light traps or sticky traps can be used indoors, though eliminating the source of the infestation remains the only long-term solution.