Why do flies rub their hands together?

If you’ve ever closely observed a fly, especially when it lands on your food, you might have noticed that they often rubs their hands together. But while it is simply flying, it rarely does so. So, what is it about sitting on food that makes a fly rub its hands?

Cleaning

The main reason why flies rub their hands together is to clean themselves.

Due to their propensity for lurking around dirty and grimy areas, flies are often covered in filth. However, this doesn’t necessarily make them dirty creatures because flies take their grooming very seriously which is obvious from them repeatedly rubbing their hands together. This gets rid of any physical or chemical detritus and cleans their smell receptors, which in turn helps them fly better, find food easily, and attract or search for mates.

The common housefly, Musca domestica, is the most representative of the entire taxonomy of flies. This fly also rubs its hands to clean itself. In fact, the cleaning process of this housefly as well as multiple other species is so thorough, systematic, and effective that an academic study proposed to teach kindergartners about personal hygiene using the examples of flies!

Interestingly, flies are not the only insect to rub their limbs together to clean themselves. Many other species of insects do so as well and give particular attention to their antenna during the cleaning process.

Now that we’ve explored in depth the cleaning behavior of flies and the role of rubbing their hands in it, it is important to establish that this is not the sole reason why flies do so. In fact, there are a number of other reasons why flies rub their bodies and each of them serves a special purpose to them. Let’s consider a few of them.

Flight Preparation

While it might seem a bit weird that flies rub their hands and legs before they fly, there is a proper connection between the two actions. Rubbing their legs or hands helps flies to plan their flight better and prepare psychologically for it. Here’s why.

By rubbing their limbs together, flies make sure that the hair on their chest and limbs are in the optimal position to assist with their flight. Since their hair acts as vestibular, the right position aids flies in balancing themselves well before they take off. Also, since the hair also provides them guidance regarding the location of their limbs, it helps them in directing their flight better.

Protection

How can the mere act of rubbing their legs or hands, and in turn cleaning, help flies protect their bodies?

What flies essentially do is fold their legs over their mouth in an attempt to remove the hair position on their heads. Research claims that hair close to the eye can divert about 90 percent of ventilation away from the eyes. Since the hair on this part of the body is arguably the most important for flies, they groom it well to protect their bodies.

Taste Sensors Cleaning

If you’ve ever been annoyed by a housefly landing on your food, you probably would have been more annoyed at the fact that it kept walking over your food instead of just sitting at one place. This is because flies ‘feel’ the food using their limbs by walking over it.

Flies often do this and particularly with food that is hard. Since it is difficult for flies to consume hard foods, they walk and stop repeatedly to check different parts of the food to find a soft region, especially one that is decaying, to eat. And even then, they might not be able to start eating right away. This is when they vomit saliva over a particular area of the food to decompose it enough for their consumption.

Throughout this process, the taste sensors of flies help them in locating hard, soft, and decaying parts of the food and figuring out how best to eat the food. The rubbing motions allow them to clean their taste sensors.

Injury Detection

By rubbing their hands or legs together, flies check the condition of their limbs. This helps them gauge how ready their body is for flying, fighting, or other activities. Additionally, these rubbing motions can help detect an injury on the body.

Since flies check the readiness and health of their limbs by rubbing their limbs together, it comes as no surprise that before getting close to other flies they sometimes do so in case they need to get into a fight.

Heat Dissipation

Like most living beings, in the face of extreme heat, flies look for cooler places or shelter. In case they can’t find one or even if they do and they are still too hot, they rub their hands and legs together to settle their hair in a way that allows maximum heat to dissipate from their bodies. This increases the surface area from where heat can leave their bodies.

Why do flies rub their legs together?

The hands aren’t the only part of the body flies rub often. They rub their legs together (often hind legs) as well for more or less the same reasons they rub their hands for. In fact, for optimal cleaning, flies rub their legs and hands both. Also, they rub these body parts against their heads and wings as well to ensure they are fully clean.

Conclusion

If you observe a fly for a while, you might notice it rubbing its hands (or legs) together or against some other body part. This is primarily to clean itself since a fly comes in contact with dirt and bacteria all day long. However, a fly might also do so to protect its head region and eyes, clean its taste sensors, prepare for flying, check for potential injuries, or to dissipate heat from its body.

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