The excretory organ in insects is the malpighian tubule. Malpighian tubules are long, slender tubes in insects that are involved in the excretion of metabolic waste products, primarily uric acid. They are connected to the gut and actively transport waste products from the hemolymph into the gut, where they can be eliminated from the body. Insects do not have kidneys like vertebrates do, so malpighian tubules serve as their primary excretory organs.