Bed bug crawling on cloth. 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. The female lays approximately 300 eggs. This insect can cause skin infections due to people scratching the bites. An adult bed bug is around 4 millimetres in length.