Abstract Herein we investigate the behavior and anatomy of all larval instars of the cleptoparasitic bee, Coelioxys (Cyrtocoelioxys) chichimeca Cresson. The species is found in Central America with its host, Centris (Heterocentris) bicornuta Mocsary, one of the cavity-nesting members of the genus. The egg/mature oocyte of C. chichimeca, unusually small (like known eggs of other Coelioxys), is described, as is egg placement in the wall of the brood chamber. The anatomy and behavior of each of the five larval instars is described. The first instar develops within the egg chorion, from which the second instar emerges. The second and third instars apparently normally remain attached by their posterior ends either to the egg chorion or to the place where the egg had been attached to the cell wall. The second instar possesses an array of large spines on the outer surface of each mandible thought to rupture the thick chorion, thus allowing eclosion. Both second and third instars have modified head capsules and m...