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The larvae (maggots, white) and pupae (brown) of a fruit fly, Drosophila sp, infesting the skin of a new potato. The maggots are part of a chain of food spoilage organisms which have attacked this supermarket pack of washed potatoes. First a rot fungus moved in and began to convert the damp, starchy potato flesh into sugars. Then wild yeasts began to grow on the sugars, converting them to alcohol and to various other organic molecules. Finally the fruit flies arrived, attracted by the smell of the yeast culture, and began to lay their eggs in the decaying flesh of the potato. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR JEREMY BURGESS)