How can you determine the sex of a butterfly?

Being able to tell the difference between male and female butterflies and moths can be easily determined or difficult depending on the species.  Some species such as the Painted Lady butterfly look the same in color and markings and can only be differentiated by examining anatomical structures.  Males tend to have a more slender abdomen and females tend to have larger rounded abdomens.  Some species can be identified by differences in the shape of the forewings.  Hairstreaks are a good example of this, males have triangular forewings and females’ forewings have a more rounded shape.  Subtle wing pattern differences are apparent in the Monarch.  Males have a round black dot in the hindwing that the females do not have.  Often females are slightly larger in size than the males.  Some species exhibit sexual dimorphism, meaning that the two sexes look completely different.