Bed bug (Cimex lectularius), coloured environmental scanning electron micrograph (ESEM). This wingless, parasitic insect is relatively flat, allowing it to hide in cracks and crevices. It grasps human skin with its forelegs, pierces the skin, and injects anticoagulant and an anaesthetic containing saliva. It feeds at night on blood from its host. The female lays approximately 300 eggs. It doesn't transmit diseases but can cause skin infections from scratching bites. An adult bed bug is around 4 millimetres in length.