The excretory system consists of three regions. The basal region has three cells found within the posterior portion of the midgut. The anterior and superior cavities are formed by the bases of four Malpighian tubules. The superior cavity opens into the lumen of the small intestine. The rectum is a large but thin-walled sac that occupies the posterior fifth of the larvae. The release of waste is controlled by the rectal valves that lead to the anus. Sometimes, the larvae secrete a liquid that consists of uric acid, water and salts. These contents are often carried outside by workers and ejected, but colonies under water stress may consume the contents. In the reproductive system, queens release a pheromone that prevents dealation and oogenesis in virgin females; those tested in colonies without a queen begin oocyte development after dealation and take up the egg-laying role. Flight muscle degeneration is initiated by mating and juvenile hormones, and prevented by . Histolysis begins with the dissolution of the myofibril and the slow breakdown of the myofilaments. Such dissolution continues until it reaches the only free Z-line materials, which would also disappear; only the nuclei and lamellar bodies remain. In one study, the amino acids increase in the hemolymph after insemination.