Fly Poop: Everything You’ve Ever Wanted to Know

Flies are one of the most common and diverse animal groups, with over 150,000 different fly species worldwide. Houseflies (Musca domestica) are one of the most widely distributed fly species, having accompanied human migration to all inhabited continents and across all climates. They are rarely found far from human habitation, and their distribution is directly tied to waste, garbage, sewage, and animal feces, which serve as their primary breeding sites. Because houseflies feed on garbage, sewage, and animal feces, they ingest massive amounts of bacteria, which are then deposited into human environments through their feces. Continue reading to discover everything you’ve ever wanted to know about housefly poop.

What Does Fly Poop Look Like?

Fly poop is called flyspeck. Flyspeck is the tiny, dark-colored specks or stains left behind by a fly’s excrement or regurgitated saliva. Flyspeck is generally not highly noticeable unless you are actively looking for it or if the infestation is severe.

Can Houseflies Control When They Poop?

Houseflies cannot control when and where they defecate. They lack bowel control and generally defecate constantly, often doing so every time they land, which can be on food, pets, windows, or any other surface on which they land.

Because houseflies consume a strictly liquid diet (using saliva to liquefy solid food), their digestive systems work very rapidly, resulting in frequent, uncontrollable defecation. n addition to defecating, flies also regurgitate (throw up) stomach contents onto food to soften it, which they then suck back up.

Do Flies Spread Disease?

Houseflies are strongly suspected of transmitting at least 65 diseases, including typhoid, cholera, and dysentery. By feeding on feces, garbage, and decaying matter, they pick up bacteria on their hairy legs and bodies, which they then spread to food or surfaces when they land. A single housefly can carry up to 33 million bacteria on its body. They are associated with the transmission of more than 100 pathogens, including bacteria, viruses, fungi, and parasites.

Houseflies transmit Salmonella, E. coli, Campylobacter, and antimicrobial-resistant bacteria, among a host of others.

Is There a Fungus Called Flyspeck?

The flyspeck commonly seen on fruits is not fly feces, but the fungal disease Schizothyrium pomi. It appears as tiny, pinhead-sized, shiny black dots that often cluster in groups of 10 to 50 on the skin of fruits like apples and pears. While it looks like fly excrement (hence the name), it is a superficial plant pathogen that is primarily a cosmetic issue and rarely causes any damage to the fruit itself.