The cocoon of Lithurgus chrysurus Fonscolobe, a univoltine species belonging to the megachilid subfamily Lithurginae, was studied using polarization microscopy and topochemical methods. The aim of the study was to establish the composition and structure of the cocoon wall of this bee in comparison with reported data for other species of this subfamily. The cocoon was found to be composed by macromolecularly oriented, positively birefringent silk protein layers that acquire a complex and thicker multilayered distribution at its rear zone. Although the composition and distribution of the silk threads in this species' cocoon was considered similar to the previously described patterns for other lithurgine bees, the absence of a mucous layer, typically produced by Malpighian tubules, differed from reported data for other species of the same subfamily.