Monarchs from North America are long-distance fliers, able to travel 2,000 miles from their summer grounds to their winter homes. It takes three generations to make this astounding journey. Members of the first generation, born at summer’s end, are called migrants. Before the season is over, they feast on nectar to store up enough fuel for the long trip south. Once they take flight, they link up with other migrants. Populations from New York converge with those from areas east of the Rockies, and together, they wing their way toward Mexico at speeds of up to 20 miles per hour. Occasionally, they will glide on air currents to save energy. The migrants reach Mexico in November. At this point, the population has thinned, due to bad weather and predation by birds. But the survivors get the chance to rest, eat, and enjoy the warmth. Springtime is mating time, and shortly thereafter, the males die. Females travel north, arriving in the southern Gulf States by April. There, they lay their eggs on milkweed plants and die.
The eggs laid by the migrants eventually develop into the second generation of butterflies in the roundtrip journey. This shorter-lived population continues the northbound flight and arrives in the mid-United States by June. Now it’s their turn to lay eggs. By late June the third generation is ready to take its turn, heading north to the migrants’ birthplaces. They complete this last step of the return journey by summertime. The third generation’s eggs will become the monarch migrants of fall.
A butterfly eats mostly nectar, sap, and fruit juices. Monarch caterpillars rely on the milkweed plant. It is the milkweed that provides the caterpillars and adults with their poison—harmless to the butterfly, but an effective weapon to ward away predators.
A butterfly’s life cycle consists of four distinct stages: egg, larva (or caterpillar), pupa (or chrysalis), and adult. The life span and development varies for each species. For a monarch butterfly egg—one of hundreds that a female lays—life begins on a milkweed leaf. When the caterpillar hatches, it measures only 1/25th of an inch. Over the course of the next two weeks, the caterpillar munches the leaf nonstop. All that nutritious greenery helps it grow to a mature size of about two inches—more than 2,700 times its birth weight! Then, the caterpillar attaches itself to a branch and forms a chrysalis. Inside this protective covering, metamorphosis begins.
After 15 days, the chrysalis crumples and a beautiful monarch emerges. The butterfly waits about an hour for its orange and black-striped wings to dry and stiffen, and then takes flight. Now an adult, the butterfly can reproduce, fly in search of food, and migrate.
Some of My Neighbors
Buckeyes, painted ladies, viceroys, luna moths, bumblebees, dragonflies
Population Status & Threats
Monarch butterflies are common throughout their range. However, the population that summers in eastern North America has been dwindling. Threats include a series of natural disasters in their Mexican wintering grounds, and a loss of milkweed plants in their summer home, often a result of development.
WCS Conservation Efforts
WCS helps protect butterflies in our own backyard and around the world, by protecting the habitats where they live. The WCS-North America program helps local farmers develop practices that protect insects and promote insect diversity. In East and Central Africa, WCS field biologists have helped conduct butterfly surveys in protected areas. The data they collect can determine whether the land is healthy and good habitat for wildlife.