Danaus plexippus

​Monarch butterflies require healthy and abundant milkweed plants for laying eggs on and as a food source for larvae or caterpillars. By consuming milkweed plants, monarchs obtain toxins, called cardenolides, that provide a defense against predators. Additionally, nectar from flowers is needed for adults throughout the breeding season, migration and overwintering.

​In the fall, in both eastern and western North America, monarchs go into a state of suspended reproduction, known as diapause, and begin migrating to their respective overwintering sites. This migration can take monarchs distances of more than 3,000 kilometers and last for more than two months. In early spring, surviving monarchs break diapause and mate at the overwintering sites before dispersing. The same individuals that undertook the initial southward migration begin flying back through the breeding grounds. After several generations of monarch offspring in the spring and summer, a new generation begins the fall migration for the first time.

Monarchs begin their lifecycle as eggs, which are laid on milkweed plants and hatch after two to five days. The eggs hatch into larvae, or caterpillars, and progress through five instars over the next two weeks before pupating into a green chrysalis. An adult monarch will emerge one to two weeks later. 

Most breeding adult butterflies live approximately two to five weeks, but overwintering adults that enter into reproductive diapause can live six to nine months.

As temperatures warm at the overwintering sites in the spring, monarchs begin to breed and lay eggs on milkweed throughout their migration. The following generations breed and lay eggs throughout the summer. In the fall, monarchs enter a state where they stop reproducing, known as diapause. This allows them to focus their energy and resources on the long-distance migration and surviving the winter. Some non-migratory monarchs in warmer climates breed year-round.

Adult monarch butterflies are large and conspicuous, with bright orange wings surrounded by a black border and covered with black veins. The black border has a double row of white spots, present on the upper side of the wings. Adult monarchs are sexually dimorphic, with males having narrower wing venation and scent patches. The bright coloring of a monarch serves as a warning to predators that eating them can be toxic. 

The large and brightly colored monarch butterfly has two sets of wings that span three to four inches. Monarch caterpillars, or larvae, have black, yellow and white stripes and reach lengths of two inches before metamorphosis.   

Measurements: Wingspan: 3 to 4 inches (7 to 10 cm) Larval length: 2 inches (5 cm) 

The large and brightly colored monarch butterfly has two sets of wings that span three to four inches. Monarch caterpillars, or larvae, have black, yellow and white stripes and reach lengths of two inches before metamorphosis.   

Measurements: Wingspan: 3 to 4 inches (7 to 10 cm) Larval length: 2 inches (5 cm) 

Monarchs weigh, on average, about half of a gram, which is less than the weight of a paperclip.

Whether it’s a field, roadside area, open area, wet area or urban garden, milkweed and flowering plants are needed for monarch habitat. Adult monarchs feed on the nectar of many flowers during breeding and migration, but they can only lay eggs on milkweed plants.

For overwintering monarchs, habitat with a specific microclimate is needed for protection from the elements, as well as moderate temperatures to avoid freezing. These conditions vary between populations. For the eastern North American population, most monarchs overwinter in oyamel fir tree roosts located in mountainous regions in central Mexico at an elevation of 2,400 to 3,600 meters. Monarchs living west of the Rocky Mountain range in North America primarily overwinter in California at sites along the Pacific Coast, roosting in eucalyptus, Monterey pines and Monterey cypress trees.