Do Flies Really Throw Up on Your Food When They Land On It? Let's Dive In

Imagine yourself at a picnic, about to eat your sandwich. You suddenly spot a fly heading your way. It uses its antennae and compound eyes to find your food. The fly lands on your sandwich, and then appears to throw up!
Although it can appear gross, the fly could be simply airing out its food or spitting on yours.

The majority of the more than 110,000 fly species aren't equipped with teeth so they can't eat solid food. Their mouthparts resemble a soft straw. After they land on food, their digestive juices are released to make it liquefy into a slurpable soup that they can eat. Some flies eat a liquid diet.

Some flies reduce the amount of liquid in food they have eaten to make it easier for them to eat more. To dry out the food, they regurgitate it into vomit bubbles. They can then ingest more concentrated food once the water has evaporated.

To get the nutrients from our food, human beings don’t have to do all that spitting and regurgitating. However, you do produce amylase in your saliva which helps to digest some sandwich bread.

Amylase converts starch into glucose and simple sugars. This is why bread becomes sweeter as you chew it.

Did you know that flies can smell food and taste it without using their mouths? They use the receptors on their feet as soon as they land to determine if they are eating something healthy.

A fly may be rubbing its legs together like a customer about to eat. This is known as grooming. The fly is basically cleaning its body. It may also clean its taste sensors on its feet to better understand what's in the food they have landed on.

Do you throw away food that a fly has landed on?

Flys can land on sandwiches, but that's not all they do. Flys often land on food that is full of microbes, such as a dumpster or decaying food. If the germs aren't removed quickly enough, they can hop on to your food.

Because some microbes can cause disease, such as cholera or typhoid, this is more dangerous than their saliva. If the fly isn't there for more than a few seconds, the chances of microbes transmitting are very low. Your food will probably be fine.

Cover your food to prevent insects from landing on it. You can use simple traps to rid your home of flies. Carnivorous plants are also capable of eating the flies to control their population.

(Norbert Forsterling/Picture Alliance/Getty Images)

Above: To clean a patient’s wounds, a doctor uses sterile Maggots from Tubes.

Are flies good at anything?

Flies can spread diseases and eat food, which sounds horrible.

You might be amazed at how many flies visit flower nectar plants if you pay attention next time you are outside. Flies are an important pollinator group and help many plants reproduce.

Flies are also an important part of the ecosystem because they provide food for spiders, lizards and birds.

There are medical uses for some flies. To remove tissue from wounds, doctors can use the immature, young blow fly maggots. Scientists have been able to create new treatments for infection thanks to the release of antiviral and antibiotic juices by maggots.

Even more important, fruit flies that you might have seen swarming around your bananas have proven to be invaluable in biological research. To find cures and causes for genetic disorders and diseases, biomedical scientists all over the globe study fruit flies.

In our laboratory, we examine how insects see the world and use their vision to fly. This knowledge can be used to inspire engineers to create better robots.

Even though it can be annoying to keep flies away, you might be able to save a few pieces of your lunch.

Ravindra Palavalli Nettimi, Associate Professor of Biological Sciences at Florida International University, and Jamie Theobald Associate Professor, Florida International University.

This article was republished by The Conversation under Creative Commons. You can read the original article.