Monarch Butterflies

Photo of the Week: Why Males?

Monarchs eat milkweed when they are caterpillars. Milkweed contain poisonous chemicals called "cardenolides." The poison stays in the adult monarch's body and is a form of defense. Females have 30% more of the toxins than do males. This is why bird predators probably eat more males than females. The males are not as poisonous as the females.

It's hard to tell if some of the butterflies below are males or females. However, put your mouse over the picture to see some we have marked. The wings of male monarchs have two field marks that help you identify them: 1) they have a black spot on their hind wings and 2) the veins of the male's wings look thinner than the veins of a females' wings.