Tell me, have you ever noticed a fly rubbing its legs together and have wondered, why it does that?

Well, flies rub their legs together to clean themselves. They have to rely on their eyes, antennae and the bristles on their bodies and legs to get a sense of the world around them. 

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On one hand, the eyes play a crucial role in visual detection and on the other, the bristles help in detecting sweet (food) and bitter taste (poison substances). 

Which is why, they have to keep their sense organs clean in order to fly with precision to find food, mates and to avoid predators. 

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So, cleaning up is like a daily ritual for them. In fact, if you ever happen to watch them closely, you'll notice that they spend a long time carefully cleaning their whole bodies and you'll also come to realise that they don't just rub their legs together, they do much more than that. 

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They run their legs all over their body, including the head and the wings as it aides in collecting dirt particles from the body. After collecting dirt from their body, they rub it down. Technically, it's like bathing for them, only without the water. Got it?

Therefore, cleaning up is not only necessary for hygienic purposes, it's also needed for keeping the bristles and other sensory organs clean and damage-free. 

This is self-care of sorts in the fly universe.