Newly eclosed female in the petunia patchYou can tell she is a female Monarch because of her smokier and thicker wing venation. The male’s wing veins are narrower . The male also sports to black dots, or sacs, one on each hind wing. The sacs are filled with a pheromone, which the male sprinkles on the female during courtship. If she is receptive, the pair will mate. The pheromones are sometimes referred to by scientists as “love dust.”
In the above photo taken during the fall migration last year, you can easily see the difference. The female is on the left, the male on the right.

Please consider contributing to our online fundraiser to bring the feature length documentary Beauty on the Wing: Life Story of the Monarch Butterfly to American Public Television. Thank you!