Ultrastructure of egg chorion of castor butterfly Ariadne merione (Crammer) (Lepidoptera: Nymphalidae)

The egg chorion of the castor butterfly Ariadne merione exhibits well organized regional and radial complexity. The anterior pole or egg pole contains a micropylar apparatus bearing three circular micropylar openings and a micropylar rosette consisting of three to four rows of polygonal cells or rosette petals. The posterior pole or egg base is membranous and bears numerous pores and is firmly glued to the substrate. The egg surface bears longitudinal ridges, grooves, protuberances and several respiratory filaments bearing aeropyles. The chorion consists of the four distinct layers such as internal layer, trabecular layer having trabecular air spaces, principal layer and external layer.