Through the spring, multiple generations of monarchs grow from eggs into butterflies. Some members of the new generations continue north, laying eggs along the way. These eggs hatch and turn into butterflies that also lay eggs. In late summer and early fall, the third or fourth generation of monarchs starts to head back south toward Mexico to complete the migration their grandparents or great-grandparents started. On some days of the journey south, they travel more than 40 km (25 mi)! To save energy, they don’t flap their wings much. Whenever possible, they glide on
air currents.
Unlike monarch caterpillars, adult monarchs don’t feed on milkweed leaves. As butterflies, they get their energy by sipping sugary liquid nectar from many types of flowers. While traveling, monarchs stop by flower patches to refuel, just like people on a cross-country road trip might stop at a gas station, says Orley “Chip” Taylor. He’s an ecologist and director of Monarch Watch, a conservation program based at the University of Kansas.
Unfortunately, people are clearing grasslands where milkweed and other flowering plants grow to make room for farms and cities. This has reduced the food available for monarch caterpillars and butterflies during their migration. Recognizing the problem, many people living along monarchs’ migration routes have begun planting butterfly gardens. These contain milkweed the caterpillars need in order to grow in spring and summer, as well as flowering plants to fuel the adults’ flight south in the fall. Even a small pot of milkweed or flowers can make a difference. “Monarchs will find these tiny patches,” says Jennifer Thieme, the science coordinator at Monarch Joint Venture, a conservation organization in Minnesota.