Life Cycle of House Flies

illustration of a house fly

Life Cycle Stages

House flies are high-volume breeders and reproducers. One researcher determined if all the offspring from one house fly female survived and matured and all of her subsequent offspring survived and matured, the result would be more than a billion flies produced in one year by that one female house fly.

Reproduction by house flies is sexual in nature with the male fly inseminating the female’s eggs. House flies develop by a process known as complete metamorphosis, meaning they develop via four distinct stages:

  1. Egg
  2. Larva
  3. Pupa
  4. Adult


To begin this staged of the house fly life cycle, female adults lay their fertilized eggs individually, but lay them in a mass of individual eggs. Females will deposit up to 150 eggs at each time and space the egg laying events several days apart.

Females choose to lay eggs in almost any kind of decaying organic material, especially animal manure, garbage, and other decomposing organic matter. Eggs need moisture to develop properly and those that become dehydrated fail to hatch. The house fly egg stage only lasts about 24 hours.


House fly larvae that emerge from their egg stage almost immediately burrow into the food material where the female laid the eggs and begin feeding. House fly larvae go through 3 larval stages called instars and the entire larval stage development may only take 3 to 7 days, depending upon temperature, moisture, and protection.

The larval stage is the grub stage of the insect and while not able to fly, larvae do possess legs that enable them to move. As the larvae mature and come to the end of the larval stage they leave their food source and crawl around seeking out cool, dry, and protected places to settle into and begin the pupal stage.


If a suitable pupal development location is not readily found for this stage of the house fly life cycle, the larvae may search for a good pupal development site for 3 to 4 days. The appearance of the fly pupae is much different than the white colored larvae since pupae develop inside a hard, outer shell that protects the pupae while it changes into an adult fly.

Within a few hours after completing pupation and emerging from the pupal shell as an adult, female adults are capable of breeding. Pupal stage emergence only takes about one hour. The total time spent in the pupal stage is about 4-6 days. Pupal size is an important characteristic since the smaller pupae are mostly males, while the larger pupae are mostly females.


Generally, adult house flies live for 7 to 40 days, depending greatly upon the temperature, humidity, food availability, and other environmental conditions. Females begin laying eggs about 4-12 hours after pupal emergence.

During the entire adult stage of the house fly life cycle, females are likely to lay 5-6 batches of about 75-150 eggs spread out over several days between each batch. During her typical lifespan an adult female may produce about 350-900 eggs. Quite prolific for an insect that only lives about 15-25 days as an adult.

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