Monarch - He or She?

Although the sex of the Monarch is determined from the egg stage, it is not possible to identify it from the outside on a caterpillar, as the sex organs are located inside its body.

There are however three ways of finding out the sex of a Monarch butterfly and one way for the chrysalis. Photos below will show this.


If you check the black dots area of the chrysalis near the cremaster hook, this is where there is a difference between the male and the female.

The female chrysalis has a tiny vertical slit just below the lower pair of black dots, whereas this area is smooth in the male.

Female Monarch chrysalis - © Denise Motard
Female Monarch chrysalis
Male Monarch chrysalis - © Denise Motard
Male Monarch chrysalis

Wing pattern: One easy way of telling apart males and females for the Monarch butterfly is by checking the top side of their hind wings. The male has a black dot on a vein of that wing, whereas the female has none.

That black dot contains pheromones that are used by males to attract females, but it's not yet known if Monarchs are using that strategy.

The other easy way to determine the sex of the Monarch butterfly is by looking at their vein pattern. In the female the black veins are slightly thicker.

Female Monarch butterfly - © Denise Motard
Female Monarch butterfly
Male Monarch butterfly - © Denise Motard
Male Monarch butterfly

Another way of finding out the sex of a Monarch butterfly is by checking their abdominal tip. This is easier to do when you raise them, because you can watch the butterfly emerge from the chrysalis. At the beginning the abdomen is large and filled with hemolymph for the wings, and the wings are still small.
As you can see from the photos below, the abdominal tip of the male has a 'clasping' organ to hold onto the female during copulation. The female has a notch on the ventral side of the abdominal tip.

Abdominal tip in Monarch male butterfly has a 'clasping' organ - © Denise Motard
Monarch male has a
'clasping' organ
Monarch female butterfly has a notch at abdominal tip - © Denise Motard
Monarch female has a notch