|Abstract||The authors analyze some structural internal and external chorionic features of the egg of Osborniella guiraensis (Kellogg, 1906) and Vernoniella bergi (Kellogg, 1906), using specific technics of preparing (e.g. fracture after critical point) and photographing under the scanning electron microscope and light microscope. The particular structures here studied are: a) in the operculum, the air chambers, aeropyles and types of hatching; b) in the amphora, the differences between exo- and endochorion, and the aeropyles; c) in the chorionic hydropile, its external morphology, disposition of canals, and its relationship with the spumaline. The most significative results obtained are the following: a) The air chambers are composed by 1 and 2 compartiments in Osborniella and Vernoniella respectively. b) The micropyles open at the tip of a mountain-like elevation in Osborniella, and in Vernoniella they open at level of the floor of the internal compartiment of the air chambers. c) The structure of the spongy-like system present in the chorion of Osborniella is tentatively considered as analogous to that present in the Anoplura; externally, this system opens into small openings of different diameters. It is lacking in Vernoniella. d) The external portion of the chorionic hydropyle of Osborniella is somewhat produced beyond the posterior surface, and its internal canals are externally separated by irregular ridges. The different amount of the hygroscopic spumaline used to glue the eggs to the feathers, much larger in Osborniella than in Vernoniella reflects their different water requirements in order to maintain the hydric equilibrium of the embryo.