Mating schistosome flukes. Coloured scanning electron micrograph (SEM) of a pair of schistosome flukes mating. These flukes cause schistosomiasis (bilharzia) in humans. The male is wrapped around the narrow female (orange). These worms live in the veins around the large intestine. During mating, the male holds the female in a groove known as the gynaecophoric canal, which he forms by folding the sides of his body around her. The eggs produced by the female leave the body in the faeces, but can also form fibrous obstructions of tissues and vessels known as granulomas. Magnification: x40 when printed at 10 centimetres wide.