
The Monarch butterfly (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 has been found in New Zealand, and in Australia since 1871 where it is called the Wanderer. It is resident in the Canary Islands, the Azores, and Madeira, and is found as an occasional migrant in Western Europe and a rare migrant in the United Kingdom. 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 is similar in color and pattern, but is markedly smaller and has an extra black stripe across the hind wing.) Female Monarchs have darker veins on their wings, and the males have a spot called the "androconium" in the center of each hind wing from which pheromones are released. Males are also slightly larger than female monarchs.
The Monarch is famous for its southward migration and northward return in summer from Canada to Mexico and Baja California which spans the life of three to four generations of the butterfly.
The Monarch’s wingspan ranges from 8.9–10.2 cm (3½–4 in.).The upper side of the wings is tawny-orange, the veins and margins are black, and in the margins are two series of small white spots. The fore wings also have a few orange spots near the tip. The underside is similar but the tip of the fore wing and hind wing are yellow-brown instead of tawny-orange and the white spots are larger.
The male has a black patch of androconial scales responsible for dispersing pheromones on the hind wings, and the black veins on its wing are narrower than the female’s. The male is also slightly larger.
A color variation has been observed in Australia, New Zealand, Indonesia and the United States as early as the late 19th century. Named nivosus by Lepidopterists, it is grayish white in all areas of the wings that are normally orange. Generally it is only about 1% or less of all monarchs, but has maintained populations as high as 10% on Oahu in Hawaii, possibly due to selective predation.
Like all insects the Monarch has six legs, however it uses only four of its legs as it carries its two front legs against its body.
Natural History Museum. Butterfly Pavilion. Los Angeles. California.