A tubule that extends from the posterior part of the digestive tract which absorbs solutes, water, and wastes from the surrounding hemolymph. Each tubule consists of a single layer of cells that is closed off at the distal end with the proximal end joining the alimentary canal at the junction between the midgut and hindgut[WP,modified]. [ http://en.wikipedia.org/wiki/Malpighian_tubule_system ]