The common housefly, Musca domestica, undergoes complete metamorphosis, or holometabolism. This developmental pathway is characterized by dramatic physical changes between life stages, ensuring that immature and adult forms do not compete for the same resources. The complete cycle, from egg to reproductive adult, consists of four distinct forms. The life cycle is highly dependent on environmental conditions, particularly temperature. It can be completed in as little as seven to ten days under warm, optimal conditions, but may take up to two months in cooler environments.
The Egg Stage
The housefly life cycle begins with the egg, which is laid by the female in a location that will immediately provide food for the emerging young. These eggs are small, white, and oval-shaped, resembling tiny grains of rice, and measure about 1.2 millimeters in length. A single female housefly can lay up to 500 eggs in her lifetime, typically depositing them in batches of 75 to 150 at one time. The female seeks out moist, decaying organic matter, such as animal manure, compost, or garbage, as the site for oviposition. The incubation period is short, often lasting only 8 to 24 hours, especially in warmer temperatures, before the first larval stage emerges.
The Maggot Phase
Following rapid incubation, the eggs hatch into the larval stage, commonly referred to as the maggot. This phase is dedicated almost entirely to feeding and growth, making it the most voracious stage of the housefly’s life. The maggot is a legless, pale white, or creamy-colored creature with a cylindrical body that tapers toward the head.
The larvae burrow deep into the decaying matter where they hatched, consuming nutrients to fuel their rapid development. During this stage, the maggot must grow significantly, which is achieved through a process of molting, or shedding its skin. The maggot passes through three distinct larval instars, growing larger after each molt before reaching its full size of up to 12 millimeters long. This intensive feeding period typically lasts for about three to seven days under favorable warm conditions.
The Pupal Transformation
Once the maggot has completed its feeding and growth, it enters the pupal stage, which serves as a period of dramatic internal reorganization. The fully grown larva migrates away from the wet, feeding material to find a drier, cooler location to pupate. The maggot’s final larval skin hardens and darkens, forming a protective, reddish-brown, oval-shaped casing known as the puparium.
Inside this immobile, non-feeding shell, the larval tissues are broken down and reassembled into the adult form through metamorphosis. The puparium provides a secure environment for this complex biological transformation. The duration of this stage is temperature-dependent, generally lasting between three to six days before the adult fly is ready to emerge.
The Adult Fly
The final stage begins when the fully formed adult housefly emerges from the puparium, often using a fluid-filled sac on its head to break open the casing. The primary function of the adult stage is reproduction and dispersal, perpetuating the life cycle. The adult fly is characterized by its grayish body with four dark, longitudinal stripes on the thorax.
Adult houseflies are capable of mating and laying eggs within a few days of emerging. Females typically mate only once but store sperm to fertilize multiple batches of eggs throughout their life. The average lifespan is approximately 15 to 30 days, though this is influenced by temperature and the availability of food, especially sugar. Their mobility and feeding habits involve frequent contact with decaying matter and food sources, allowing them to act as vectors, potentially transferring microorganisms between sites.