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Blow Flies and Flesh Flies

Jeffrey Hahn, Asst. Extension Entomologist

Some people have discovered the sudden appearance of medium sized flies in their homes. Blow flies are iridescent green, blue, or coppery colored flies while flesh flies have dark colored bodies with three black stripes on their thorax and a checkerboard pattern on their abdomen. Both types of flies lay their eggs on dead animals and decaying garbage. The larvae are smooth, cream-colored, legless maggots that are carrot-shaped with the narrowest end by the head. When fully grown, they are about 3/4 inch long.

Jeff Hahn

Photo 1: Blow flies on animal remains

When a dead animal becomes trapped inside a home, e.g. inside a ceiling or wall void, and dies, it is not uncommon for it to attract these flies which lay eggs on the corpse. Eventually they turn into adult flies which can emerge into the home. It is also possible to see the maggots inside a home. As mature maggots wander away from their food source to less crowded sites to pupate, they can inadvertently move through light fixtures or other spaces and fall into the living space of a home.

These flies are generally harmless to people and property, although because of their unsanitary habits they do have the potential to spread filth-related diseases such as diarrhea and dysentery. On the plus side, they are helping us out by removing and recycling organic material.

A blow fly or flesh fly infestation will persist until the carcass is consumed. The most effective method to control them is to remove the food source, i.e. the dead animal. Unfortunately, this is usually not practical as the animal is typically trapped in an inaccessible place. Be patient and eventually the dead animal will be removed naturally by the maggots. The flies and the maggots will go away on their own once the food source is consumed. This generally takes several weeks to happen.

Click here for more information on summer flies.
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