Guide To Common Filth Flies

Flies are generally viewed as a nuisance at best, disgusting creatures of filth at worst. But how much do you really know about flies? Flies such as the common housefly are known as filth flies, and are separated into two categories: large and small. Both types of flies can spread diseases and bacteria based on their habits of feeding and laying eggs on things such as garbage piles, manure, and carcasses, then contaminating food which humans consume. Some types of filth flies, or Diptera, also bite and feed on the blood of humans and animals, spreading blood-borne diseases. Diptera, or true flies, only have two wings (or one pair) as opposed to other winged insects which have four wings (or two pairs.) Both large and small flies are drawn to moist, organic material to lay their eggs on, which makes them valuable scavengers, but causes the spread of bacteria and diseases to humans.

Large Filth Flies

Large filth flies begin their lives as maggots, growing up to have stout bodies and short legs. They prefer foods such as manure, carrion, and garbage. Large filth flies consist of house flies, blow flies, and flesh flies.

House Flies

Common House Fly

We’ve all encountered the common house fly at one time or another. This buzzing nuisance has a dull gray body that typically measures about ¼ inch long. The house fly is marked by four dark stripes down the middle section, aka the thorax, of its body. House fly eggs are typically laid on garbage or animal feces, which hatch into legless, white maggots. Maggots crawl away from their food source once they’re fully grown to undergo the pupal stage, later emerging as full-grown house flies. House flies can fly one to two miles when seeking egg-laying sites.

Blow Flies

blow fly

Blow flies get their name from the way their larvae develop inside the carcasses of dead animals. This causes the carrion to have a bloated appearance. Blow flies are the same size as house flies, sometimes larger. They are attracted to garbage. Blow flies have a shiny blue-green sheen, which has earned them the nickname “bottle flies,” as their color resembles that of old glass bottles. Large swarms of blow flies usually means a dead animal is somewhere nearby.

Flesh Flies

Flesh FlyFlesh flies seek carrions or raw meat to lay their eggs, which is how they got their name. Adult flesh flies are dark gray or black, and typically have three dark stripes down their thorax. They are larger than house flies and have an interesting checkerboard pattern on their abdomen.

Small Filth Flies

Small filth flies begin their life cycle as maggots or small worm-like creatures. Once they’ve hit maturity, they have slender bodies and long legs. They feed off of drain sludge, organic debris, and rotting plants.

Fruit Flies

Fruit Flies

Fruit flies, aka vinegar flies, are attracted to sweet or fermented liquids. They are especially fond of liquor, syrup, soda, vinegar, and rotten fruit. Females lay their eggs in these materials, which provide a food source for their larvae. Adults are gnat sized with tan bodies and red eyes.

Phorid Flies


Phorid flies are also known as humpback flies due to their arched thorax. These tiny, dark-colored flies begin their lives as larvae feeding on decomposing organic materials, of plant or animal origin. When enough food resources are readily available, phorid flies can build in population very quickly. They commonly infest things such as liquefied garbage, sewage, carrion, which are often hidden out of the way where it’s difficult to access.

Drain Flies

Drain Fly

Adult drain flies are slightly larger than other small filth flies, measuring in at 1/8 inch. They have broad, hairy wings, which have earned them the nickname of “moth fly.” They are also commonly known as sewer flies, since they frequent areas that contain raw sewage. Drain flies often hang out on bathroom walls, although their larvae live submerged in the gelatinous muck that accumulates on bathroom floors, sinks, and toilet drains. Drains and traps should regularly be cleaned to avoid infestations. 

Fungus Gnats  

Fungus gnat (Sciaridae)

Fungus gnats resemble small mosquitoes, with their long, delicate legs. The larvae live in moist places where fungus grows, as this is what they survive off of. Over-watered potted plants that have grown fungus are prime places for infestations to occur.  

Managing Filth Flies  

When managing filth flies, sanitation is key. By eliminating fly breeding grounds, you can prevent fly infestations. If you are currently experiencing an infestation of some form of filth fly, call a pest control professional. Once you’ve gotten the infestation under control, take preventative measures to avoid future outbreaks.

About the author:

Chris is a blogger for Excel Pest Control a NJ based pest control company.

Published Thomas Ballantyne


Thomas Ballantyne is the Director of Marketing with Bulwark Exterminating, an industry leader in providing high quality pest control service. Bulwark is fully operational in seven states, including twelve major cities. While Bulwark provides pest extermination for common insects such as ants, roaches, crickets and spiders, the company’s differentiating aspect is great personalized service. Bulwark uses the finest and most effective products in the world to solve common pest problems.

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2 thoughts on “Guide To Common Filth Flies

  1. Flies are completly filthy. People do not realize how much disease they carry and spread. They ruin barbecues!

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