Insects excrete waste through an anus, just as most other animals do. Insects have complete digestive systems, meaning that food travels in one direction through a continuous tube, called the alimentary canal. This contrasts with animals that have two-way digestive systems, such as starfish, anemones and jellyfish. Complete digestive systems allow for specialization of the structures, leading scientists to consider them more advanced than two-way systems.
Insects eat food through their mouths, which vary in structure according to the type of food they eat. The food then passes through the foregut, where salivary glands help lubricate the item. It is further digested as it passes caudally through the midgut and then the hindgut. The rectum exits the back of the abdomen through a structure called the anus.
Insects are efficient with water. When digested food passes into the rectum, up to 90 percent of the water is reabsorbed to prevent dehydration. Rather than producing urine, insects use a system of structures called Malpighian tubules to remove nitrogenous wastes from the insect’s body. The Malpighian tubules deposit the waste products into the alimentary canal, at the junction of the midgut and hindgut. The waste products are then eliminated along with the feces.