The term “green fly” refers to two distinct types of insects, meaning there is no single, simple answer to its lifespan. The lifespan depends entirely on the specific organism referenced, as their biology and life cycles differ. For the winged insect most commonly recognized as a “green fly,” the total time from egg to the end of its adult life averages only a few weeks. The duration of each life stage is highly changeable, meaning the total lifespan can vary significantly based on the surrounding environment.
Defining the Term Green Fly
The common name “green fly” causes confusion because it describes two insects from different scientific orders. The first and most likely candidate is the Green Bottle Fly (Lucilia sericata), a true fly belonging to the order Diptera. This insect is recognizable by its striking, metallic-green or blue-green body, measuring about half an inch long. The second insect commonly called a “greenfly” is an aphid, such as the Green Peach Aphid (Myzus persicae), belonging to the order Hemiptera. Since the search query implies a flying insect, this discussion focuses on the life cycle and duration of the Green Bottle Fly.
The Stages of Life and Typical Duration
The Green Bottle Fly undergoes complete metamorphosis, a process involving four distinct stages: egg, larva, pupa, and adult. Under ideal conditions, the entire cycle from a newly laid egg to an emerging adult can be completed in as little as 10 to 25 days. The female fly initiates the cycle by laying clusters of up to 200 whitish eggs, often on decaying organic matter or carrion.
The egg stage is brief, lasting anywhere from nine hours to three days, with warmer temperatures accelerating the hatching process significantly. Upon hatching, the larva (maggot) begins its primary feeding and growth period, passing through three stages, or instars. This larval phase typically lasts between three and ten days, during which the maggot consumes massive amounts of protein to store energy for the next stage.
Once fully grown, the larva leaves its food source to find a protected location, usually burrowing into the soil to begin the pupal stage. The pupa is encased in a hard, dark shell, and this phase of transformation lasts approximately 6 to 14 days. Finally, the adult fly emerges from the pupal case, and after its wings and exoskeleton harden, it enters the final life stage.
The lifespan of the adult Green Bottle Fly is short, averaging about two to four weeks. During this period, the adult focuses on feeding on nectar and fluids for energy, mating, and laying eggs to start the next generation. A single female can produce thousands of eggs in her lifetime, ensuring a rapid turnover of generations throughout the warmer months.
Environmental Factors Affecting Lifespan
Temperature is the most important external factor governing the Green Bottle Fly’s life duration, particularly during developmental stages. Warmer temperatures drastically speed up the metabolic rate of the larvae, shortening the time required for them to mature. For example, the entire larval development can take only three days at 27°C, compared to over a week at cooler temperatures.
The availability of a suitable food source is necessary, as the larvae rely on a rich supply of decaying matter to complete their growth. Low humidity or a lack of moisture can slow development or increase mortality, particularly for the delicate eggs and newly hatched larvae.
When temperatures drop in cooler climates, the life cycle may be paused through a process called diapause. During diapause, the pupa or, less commonly, the larva enters a state of dormancy, allowing it to survive the cold winter months. This pause can extend the time between generations by several months, even though the adult fly’s active life remains limited to just a few weeks.