Monarch Butterfly : Introduction

The monarch (Danaus plexippus) is a milkweed butterfly (subfamily Danainae), in the family Nymphalidae. It is perhaps the best known of all North American butterflies. Since the 19th century, it is also found in New Zealand, and has been known in Australia since 1871. In Australia it is also known as the wanderer butterfly. In Europe it is resident in the Canary Islands and Madeira, and is found as a migrant in Russia, Azores, Sweden, Spain and Portugal. Its wings feature an easily recognizable orange and black pattern, with a wingspan of 8.9–10.2 centimetres (3½–4 in). (The viceroy butterfly has a similar size, color, and pattern, but can be distinguished by an extra black stripe across the hindwing.) Female monarchs have darker veins on their wings, and the males have a spot in the center of each hindwing from which pheromones are released. Males are also slightly larger.

Monarch butterfly
Female	Male

Reference：

http://www.maolin-nsa.gov.tw/maolin/index.php?lang=ct&style=style2