英语听力：自然百科 虫虫兄弟—17（在线收听）

 They dive in, feet first, tasting food with sensors on their feet. Once they've selected a mouthful, they'd salivate over it, eat it, then regurgitate it to break down any chance. They then suck up the foul soup they've made with their spongy mouth parts. This is how the watery waste looks under the scanning electron microscope. And house flies don't even stop eating when they have sex. In fact, females like to do both almost constantly. Fortunately flies usually live only about three weeks. In 1911, a scientist called C.F. Hodge estimated that if flies didn't die, one pair beginning to breed in April could be responsible for over 200 million trillion flies within a year, enough to cover the earth with a layer of flies almost a meter deep. Under the kichen floor boards, a new generation of flies engages in frenzied eating. It's the corpse of another mouse. Flies maggots are non-stop eating machines. If it's dead, they'll eat it. They shred corpses and rake in the rotten flesh with hooks in their mouth. To help keep gorging, they even breathe from behind through tubes near their anus so their front ends can keep on eating. As fly maggots only eat dead flesh, specially bred sterol ones are sometimes used medically to heal septic worms. It's believed that maggots devour the infected flesh, leaving the healthy tissue alone and even excrete sterilizing substance.