V. H.  Gonzalez, Palacios, E., and Trujillo, E., ?Nesting habitats and rates of cell parasitism in some bee species of the genera Ancyloscelis, Centris, and Euglossa (Hymenoptera: Apidae) from Colombia?, Bolet{\'?n del Museo de Entomolog{\'?a de la Universidad del Valle, vol. 8, 2007.