Egg structures of four Nabis species (Rhynchota : Nabidae)

Despite the numerous works on insect egg structure, detailed studies on Nabis genus (Rhynchota : Nabidae) have not been carried out previously. The external morphology and internal chorionic structure of the eggs of Nabis pseudoferus pseudoferus Remane, Nabis occidentalis Rieger, Nabis punctatus Costa and Nabis rugosus L. were investigated, using scanning electron microscopy, to improve our knowledge of their organization. To assess their role in taxonomy, a comparison between the eggs of the 4 species under consideration was carried out. The eggs are jar-shaped with the front end narrowed in a “collar” and closed by an operculum. The chorion, except in the regions of the collar and the operculum, is organized in an outer layer of about 4–5 μm, separated from the inner surface by a “pillars” layer of about 0.5–1 μm. In the region of the collar, the chorion has small internal channels which represent the aeropyles; their number varies very considerably even within the same species. The operculum is made up of closed spaces filled with air in communication with the aeropyles and the “pillars” layer, thus forming a single space that represents the respiratory system. The general shape and characteristics of the eggs of N. pseudoferus, N. occidentalis and N. rugosus are very similar; only N. punctatus can be identified with certainty at the egg stage.