Mason. The females construct their exposed nests on stone and rock surfaces, in rock crevices, or occasionally on twigs (Rebmann 1969, Vereecken et al. 2010). The cells are made of a cement which is a mixture of sand, particles of earth, small pebbles and saliva. The nest consists of 6-20 cells, covered with a common layer of mortar. The external surface of the cells is rough, but internally, they are highly polished. (Banaszak & Romasenko, 1989)