SUSUMU NISHINAGA Honey bee excretory system. Coloured scanning electron micrograph of part of the excretory system of a honey bee (Apis mellifera). The convoluted Malpighian tubules (light brown) are responsible for the excretion of nitrogenous waste. They selectively extract water, salts and nitrogen-containing uric acid from the bee's blood. The tubules empty into the gut (intestine, pink) of the bee, and the waste is expelled from its body in the faeces.