Mason bee (Zoöl.), any one of numerous species of solitary bees of the genus Osmia. They construct curious nests of hardened mud and sand. -- Mason moth (Zoöl.), any moth whose larva constructs an earthen cocoon under the soil. -- Mason shell (Zoöl.), a marine univalve shell of the genus Phorus; -- so called because it cements other shells and pebbles upon its own shell; a carrier shell. -- Mason wasp (Zoöl.), any wasp that constructs its nest, or brood cells, of hardened mud. The female fills the cells with insects or spiders, paralyzed by a sting, and thus provides food for its larvæ