Blowflies are usually found near decaying material. Adult blowflies deposit their eggs in the decaying material. Carcasses of dead animals are the locations that they prefer. Many times people find blowflies in the home. This often happens when the flies discover a dead squirrel, mouse, or bird that the homeowner had not seen.
Around homes, the garbage cans are also favorite blowfly breeding sites. The flies will also deposit their eggs in animal droppings. Some blowflies will enter homes. If meat or other food it exposed, the flies will even deposit their eggs in it.
When they come out of their eggs, blowfly maggots begin to eat the material where they hatched. They do not have eyes or legs, so they cannot travel to other foods.
As they grow, the maggots burrow down into the material. Depending on the species, the blowfly maggots can finish their larva stage in as little as two weeks. However, for some species, the larva stage can last as long as a month.
As they grow, blowfly maggots must shed their skin two or three times. When they are fully grown, the maggots can be almost one inch long. They are whitish in color. The body is tapered with the wide end toward the rear. There is a pair of dark hooks at the head-end of the body.
In the last part of the larva stage, the maggots crawl out of the food material where they have been living. They burrow into the soil where they change into adult flies. Larvae that develop late in the summer often spend the winter as maggots or in their pupal case.
Scientists have discovered a way that blowfly maggots can actually be beneficial to humans. Some species of blowfly maggots are used as “surgical maggots”. Doctors use specially grown maggots to clean infected wounds. The maggots remove the infection and cause the wounds to heal faster than they would otherwise.
Blowfly larvae grow and develop into adult flies. Many people call them maggots. The female flies deposit their eggs on decaying material. When the eggs hatch, the blowfly larvae eat the decaying material.
Blowflies prefer to deposit their eggs on the carcasses of dead animals. Sometimes the flies find a dead squirrel, mouse, or bird around a home. The flies will search out the animal in the attic, the chimney, or the rain gutters.
Many times the flies make their discovery before the homeowners do. For many homeowners, the flies are the first clues that an animal was even nearby.
If there is not an animal available, the blowflies will readily deposit their eggs in garbage cans. Scientists have reported finding thousands of blowfly larvae in one garbage can.
Each time the larvae molt, they grow larger. After the last molt, the larvae can be almost one inch long. They are whitish in color. They have no eyes and no legs, so blowfly larvae do not travel far.
As they grow larger, the larvae burrow deeper into the material where they are feeding. The larvae can finish developing in two weeks. However, some species take more than a month for the larva stage. Unfavorable temperature can make the larva stage last even longer.
When they are fully grown, the larvae move out of the food material and burrow down into the soil. The larvae are ready to change into adults. In the summer, the change into adults takes 3 days to two weeks, depending on the species. In the fall, the larvae burrow into the soil and wait until spring to change to adult blowflies.
People who try to eliminate blowfly larvae by spraying the adult flies are usually disappointed with the results because the flies do not go away.
Homeowners who find blowfly larvae should eliminate the material that they are eating. Removing the breeding site will break the life cycle, so no more blowflies will develop.
Sometimes homeowners must call on a pest control professional for help in finding the source of the larvae, especially if it is in a hidden location like the attic or inside of a wall.
The larvae can be removed with a vacuum cleaner. They can also be killed with an aerosol insecticide. Adult flies can also be vacuumed from windows indoors.