Grid formation in hornet cuticle induced by silk spun during pupation

Examinations carried out via atomic force microscope (AFM) on the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae) revealed, on the cuticle of the gaster in the region of the yellow stripes, flats bearing a grid in the form of parallel strips. Such configurations, of the same dimensions, were obtained also by superposition imaging of the longitudinal fibrils in the pupal silk weave, which are comprised of a central fibril of fibroin and an outer coating of sericin. In the latter instance, the configurations were revealed in regions where the outer coating of the fibers was disrupted or occurred only intermittently. We conjecture that the silk fibers and flats which encase the 5th-instar larva as it pupates in the dark somehow exert an effect on the morphology of the epicuticle in the metamorphosing pupa and that the effect is achieved via irradiation of heat waves, by an electric charge, or by the induction of a magnetic field. We discuss the possible implications of the presence of grids on the cuticles of adult hornets and also their possible connection with solar cells and light polarization.