About Monarch Butterflies

Monarch butterflies in North America are in serious trouble. Populations of monarchs have decreased over 90% since the mid 1990s. This decline could result in the end of the monarch migration if the current trend continues. The Ned Smith Center for Nature and Art is currently developing a program that will hopefully help to reverse the current monarch population decline.

Click here to learn more about how YOU can help!


Monarch butterfly eggs clustered on a milkweed leaf.

Monarch butterfly eggs clustered on a milkweed leaf.

Monarchs and Milkweed

Simply put, monarchs need milkweed.  A female monarch will only lay her eggs on one of the many varieties of milkweed. Here in Pennsylvania, the native varieties include common milkweed, ornamental milkweed and swamp milkweed.

Click here for a helpful state-by-state list of milkweed species.

The natural world is already tough on monarchs: less than 2% of a female monarch’s eggs survive to the adult phase.  Habitat loss is a major cause of the recent precipitous decline the monarch has experienced.

About Monarch Butterfly Migration

Monarchs can migrate to the wintering grounds in Mexico from as far north as southern Canada. A female monarch that emerges from her chrysalis in late August will defer the breeding stage and go into the migratory mode, a phenomenon that is thought to be caused by cooling fall temperatures and decreased light.

Map of monarch migration patterns.Image courtesy of monarchwatch.org

Map of monarch migration patterns.
Image courtesy of monarchwatch.org

In six weeks to two months she will fly a thousand miles through the United States into Mexico, where she ends her journey at the high volcanic mountains west of Mexico City. These mountains can be as high as 11,000 feet in elevation, and provide exactly the right climate and humidity. She will then wait until the middle of March, when spring weather conditions make it safe for her to fly back to the south central part of the United States (another thousand miles!) in order to lay her eggs.

She dies, but her offspring — considered to be the second generation — continue the northward journey. They fly to the central part of the United States where they lay their eggs (the third generation) and die. The third generation then flies to the northern part of the United States and Canada where they lay their eggs and die. The fourth generation which is (known as the super generation) then flies to Mexico, starting the cycle all over again.

On the journey north, monarchs need milkweed and flowering plants. On the flight down to Mexico, monarchs need flowering plants to provide them with the necessary nourishment. Lack of flowering plants and milkweed on monarchs’ migratory journeys can have drastic consequences for these amazing creatures.


Ned Smith Center