Blow Flies: Life Cycle & Facts

Instructor: Sujata Archer
In this lesson, you will learn about the life cycle of the blow fly, an insect that not only has become famous in crime scene investigations, but also has many other functions.

The Life Cycle of Blow Flies

There is a crime scene investigation going on near an alley. A murder has been committed, and the police have to determine at what time the crime took place. The forensic scientists decide to look at the blow flies on the deceased body to come up with a time for the murder. But what are blow flies, and how can they help solve a murder?

Blow flies belong to the Calliphoridae family of insects in the order of Diptera (insects that have two wings). Their genera include Chysomya, Lucilia, and Calliphora. They tend to be larger than house flies but share very similar habits. They come in green, blue, copper, and purple colors. Some familiar names for blow flies are bluebottle, green bottle, or screwworms.

Blow flies thrive best in weather that is warm and humid. They do not do well when there is wind, extreme dry climate and heat, or cool weather. These conditions are important for the life cycle of the blow fly.

The life cycle of the blow fly occurs in six parts.

  1. First, the eggs are laid, especially at wound areas or around openings, such as the eyes, ears, and nose.
  2. Next, the eggs hatch into first-stage larvae (maggots) within 24 hours.
  3. The larvae feed and molt into second-stage maggots.
  4. After more feeding, they molt into third-stage maggots.
  5. Finally, they become pupae on the ground.
  6. Last, adult blow flies emerge to begin the process again.

The life cycle of the blow fly begins when the female lays eggs. Approximately 250-300 eggs can be deposited by one female, usually done over winter. The life cycle takes two to three weeks to complete.The female blow fly has to consume some protein before she can mate, whereas the male blow fly is sexually mature when it is born.The eggs are usually laid in openings of a cadaver or wounds. The larvae then feed on the decaying material. It then takes 24-48 hours for the eggs to hatch.

The life cycle of a blow fly
Life Cycle of a Blow Fly


Blow flies have proven to be very good survivors. If blow fly larvae (plural for larva) find themselves in a lighted area, they at once retreat to darker spots.This is done so predators cannot see them and interrupt their food supply.

The larvae of a blow fly are only 1 to 2 mm when they are born. However, by day 3 or 4, they are 1 cm in length. The maggots secrete an enzyme that can break down protein, and this allows them to consume semi-liquid material from a carcass!

Helpful or Harmful?

The green bottle blow fly is used for medical purposes. The larvae of this blow fly does not consume healthy tissue and only eats decaying tissue. The larvae are used for maggot debridement therapy (MDT). This treatment is for diabetics who have wounds that do not heal. A research study reported that the maggots actually helped heal the wounds by altering their pH, thereby inhibiting bacterial growth.

The green bottle fly
greenbottle fly

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