Room 3, of Balclutha School, asks :-
How can we tell the difference between a male and a female monarch butterfly?
Brian Patrick, a entomologist at the Otago Museum, responded.
The males and females of most species of animal look and behave differently because they perform different roles for their species and are usually distinguishable by sight. In some cases only experts can separate them, but many, such as the monarch butterfly, are more easily separated after a little practice.
Female monarch butterflies have broader black lines on all of its wings, while the males have a distinctive black patch of scales beside one of the black veins on the hindwings. This patch on the male is called a "sex patch" and is actually a pouch that is open to the upper surface of the wing. Although its exact role in courtship is not known it is believed to play a role such as temporary storage for pheromone (perfumes) released by the male to attact the female.
Courtship in insects is surprisingly complex and very rewarding for anyone who takes the time to observe it in its entirety. Courtship in monarchs is a four-stage event, which can last up to 15 hours. It includes energetic wrestling while the male attempts to clasp the tip of the female's abdomen with his own, stroking of her antennae and head with his antennae and the transfer of a spermatophore (packet of sperm). The female uses sperm in this spermatophore to fertilise the eggs as she lays them. She may lay up to 700 eggs during her lifetime, each laid on the correct larval host plant and "glued" to the swanplant with a special adhesive.
A useful book for further reading on this and other aspects of the monarch's life history is "The Monarch Butterfly" by George Gibbs (1994).