Samantha Fox, of Ardgowan School, asks :-
Why do flies rub their legs together?
Simon Pollard, an entomologist at the Canterbury Museum, responded.
When a fly lands on a piece of food, it `tastes' the food with its feet. Special sense organs on its feet can tell the fly what type of food it has landed on, and whether it can eat it. It is very important for a fly to keep its feet clean, so it can identify what it has landed on. In the world of flies, tiny particles, like pollen grains, dust - which is mostly bits of dead skin, bits of dead insects etc, can become stuck to the fly's body, and especially the feet, when the fly is walking around.
Flies, by rubbing their legs together can clean off these tiny particles. Imagine if your feet became covered in oranges and you had to brush them off with your hands. Flies also clean other parts of their bodies, like their eyes, by brushing over them with their legs. In rainforest in Borneo I have seen flies which have their eyes on stalks. They clean their stalks and eyes, by hanging the tips of their front legs over the stalks and moving them up and down the length of the stalks and over the eyes. It is not surprising that these flies are called stalk-eyed flies.
Flies can look like skilful gymnasts, as their twist their bodies and contort their legs so they can clean them. Flies will also use their mouths to clean their legs, and pull each leg through their mouthparts to remove dirt, and probably eat the bits that are edible.