It can be difficult to tell the difference between male and female insects, except if they look very different – i.e. when they are dimorphic.
When male and female animals look the same or similar, they are monomorphic.
Many, in fact most, species of butterflies are dimorphic, so it is easy to spot a male and a female. For example, the Common Birdwing Butterfly (Troides helena) male and female look different. The male has black wings with yellow on its hind wings (back wings) and one or more black spots, with a black body and yellow belly. The female has more obvious veins in her wings and her hind wings have a series of large, oval black spots. Her belly is dark-brown.
The Zebra Longwing Butterfly (Heliconius charithonia) is monomorphic. The wings of both the male and female are black with narrow white or yellowish stripes.
If butterflies are monomorphic, take a closer look and you might see slight or subtle differences.
Usually, male butterflies have a slimmer body than the female. The female has a rounded abdomen, whereas the male abdomen is flatter, or straight up and down. For example, the male Monarch Butterfly has a black dot near the bottom of each of their hind wings, whereas the female has no black dot.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM