University of Maryland Extension


Life stages of a house fly
House fly life cycle

House flies 

  • The most common fly found in and around homes.
  • The adults are about 1/4 inch long and dull gray.
  • The larvae or maggots are 1/4 to 3/8 of an inch long when mature. They are whitish, eyeless, legless and taper towards the front.
  • Food varies from excrement to human food.
  • Adults use their mouthparts to liquefy and pick up food and can mechanically transmit many disease pathogens.
  • Female flies will seek out any warm, moist material that has sufficient food for larval development.


  • Locate larval breeding sites to clean up the area and/or eliminate them.
  • Timely removal of trash and keeping garbage cans as dry and clean as possible is important. Use cans with tight-fitting lids.
  • To prevent adults from entering homes, tighten screens, windows, and doors. Seal all holes and entry points. Make sure all vents are tightly screened.
  • Adult flies can be trapped with baited fly traps or sticky fly tape.
  • Spraying is generally not effective or recommended inside the home. 

Blow Flies, Greenbottle, and Bluebottle Flies

blow fly
Blow fly
Photo: Dr. Mike Raupp

close up green bottle fly
Greenbottle fly

blue bottle fly closeup
Bluebottle fly

  • Blow flies and bottle flies are similar in size to house flies but are metallic blue or green.
  • These flies may breed in dead animals, feces and/or garbage depending on the species.
  • If a large number of these flies are found in the house, they are usually breeding in the home or in the immediate area.
  • Examples of breeding sites may be a dead mouse or squirrel in the attic or a dead bird in the chimney. The green bottle flies are commonly seen on pet feces outdoors.


  • The life cycle is very short (2-4 weeks). So, as with the house flies, it is important to locate and eliminate the larval breeding site.
  • This may involve timely removal of pet waste from the yard, locating a dead animal, or cleaning up garbage cans.
  • Adult control is the same as for house flies.

Rev. 2020

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