Coelioxys

Like Megachile, genus Coelioxys lacks arolia, but is readily distinguished from Megachile by the produced and acute axillae. The thorax is robust, but the metasoma tapers posteriorly and is quite elongate. Additionally, Coelioxys has the eyes hairy in the American species, a character not shared by Megachile. This genus is world-wide in distribution and is parasitic in the nests of other bees, principally those of the genus Megachile. The females lay their eggs in the Megachile cells, and the young larvae destroy the young Megachile, then feed on the stores provided by the Megachile.( The megachiline bees of california)