What's sexual dimorphism?
Males and females of the same species may differ dramatically in wing coloration from each other. Such species are said to be sexually dimorphic. In many species, sexual dimorphism is not present or extremely subtle while in others, it may only be an obvious but consistent difference in wing coloration and pattern between the sexes of the same species.
The Orange-tip has one of the most obvious examples of sexual dimorphism. The males, have orange-tips to their wings, this coloration being completely absent in the females (see photos right).