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Wasp sting. Coloured scanning electron micrograph (SEM) of the sting of a wasp. The sting is a modification of the female ovipositor, or egg-laying organ. It is no longer used to lay eggs, but instead serves as a weapon of defence and attack. The sting consists of a lancet, with a venom sac at it base and attached muscles. When not in use the sting is encased in the abdomen. Magnification: x65 when printed at 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY)