The Great Eggfly (Hypolimnas bolina), also called the Blue Moon Butterfly in New Zealand or Common Eggfly, is a species of nymphalid butterfly.
Hypolimnas bolina is a black-bodied butterfly with a wingspan of about 70–85 millimetres (2.8–3.3 in). The species has a high degree of sexual dimorphism. The female is mimetic with multiple morphs.
The upper side of the wings of the female is a brownish black and does not have any spots like those of the male. The edges bear white markings which are similar to those of the Common Indian Crow.