Danaus plexippus plexippus
In California, the Monarch is best-known for its annual migration to the coastal groves where it roosts in clusters that have long been a tourist attraction. Monarchs east of the Rockies migrate to and from roosting sites in Mexico. In our area, movement is generally northward towards Canada and back as temperatures allow (they don't do well in freezes). Where I live, freezes aren't an issue most years, and we have Monarchs all year. The larvae eat milkweed leaves and flowers, many of which contain poisons that make most of the adult butterflies distasteful to predators.
This is an excellent butterfly to attract to a garden, simply by planting milkweed Asclepias species - preferably a native. For California, good choices include fascicularis, speciosa, eriocarpa, cordifolia, and californica. I always have some in the garden, and can't imagine not having at least a Monarch or two present and lending the garden a more dignified air.
This Monarch is nectaring on host milkweed at El Dorado Park, August 5, 2005.
Freshly emerged in my garden, May 25, 2010.
A male Monarch at El Dorado Park in a patch of milkweed, August 5, 2005. Males have thinner black lines along the wing veins and a patch of black scales on each hind wing.
A female Monarch that had recently emerged from her pupa in my garden in Long Beach, October 26, 2005. One benefit of raising them yourself - fresh models!
Starting in 2005 I began planting plenty of Milkweed in my garden to attract Monarchs. This worked well, and I have watched them go through their life cycle many times. This is a Monarch egg on Milkweed.
A first instar Monarch caterpillar that had recently emerged from an egg. April 13, 2011.
Second instar Monarch larva on the same plant as above, April 17, 2011.
A Monarch caterpillar on its foodplant. This milkweed is curassavica, which works but isn't recommended.
A Monarch pupa.
Another Monarch pupa not long before the emergence of the adult butterfly.
The naming by Linnaeus. Plexippus
was placed within the Danai, one of six divisions ("phalanges", probably meaning a phalanx or unit, from the military units in the Greek armies) within Papilio, which was within the Lepidoptera. Within the Danai, Linnaeus had two further divisions: the Candidi and Festivi, characterized by wings white and variegated, respectively. The butterfly had been known and illustrated from the Americas, but Linnaeus was first to give it a formal name within a system of classification. From the Systema Naturae, Vol. 1, 10th edition (1758), p.471