Egg glue secretion and chorion morphology of the Southern Green Stinkbug Nezara viridula L. (Hemiptera: Pentatomidae)

Insect egg glue plays a crucial role in adhering eggs together and to the substrate, thus providing them protection and stability. In most insect species, the glue is secreted by the accessory glands in the female reproductive tract, known as 'colleterial glands'. However, in Nezara viridula L. (Hemiptera: Pentatomidae), these glands are absent, leaving its production site unclear. Through light microscopy, Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM), a distinct glue layer was identified between the follicular cells and the mature eggs in the vitellarium region, extending to the pedicel region of the ovariole. Ultrastructural analysis revealed that follicular cells contained numerous glue-filled vesicles, indicating that they actively secrete the egg glue via microvilli. During oviposition, the barrel-shaped eggs are laid in clutches with glue at their bottom and lateral sides. The glue subsequently hardens to form a cement-like layer that secures the eggs to the substrate. This glue adapts to the surface, faithfully replicating its features. N. viridula eggs show chorion decorations with conical projections and aero-micropylar processes along the circumference of the operculum. Mushroom-shaped structures are present around the aero-micropylar processes, making this area unwettable. The aero-micropylar processes vary in number and have porous texture with the opening for sperm entry in the apical part. This study, together with further investigations aiming to characterize the mechanical and chemical properties of the egg glue of N. viridula, enhances our understanding of the reproductive biology of this harmful insect and can have practical implications for pest control strategies and innovations in materials science.