Late summer and early fall is a peak time for monarch activity as they prepare for the long migration south to the forests of central Mexico. It’s also a great time to view them as they feed on late blooming flowers like goldenrod and aster to fuel their long journey.
Monarch butterflies have four life stages: egg, larva (caterpillar), pupa (chrysalis) and butterfly. Adult monarch butterflies typically have four generations each season. The ones most visible at this time of year are the fourth generation, which are the ones that will migrate thousands of miles to Mexico, said Stephanie Touzalin, a naturalist at the District’s Willowbrook Wildlife Center in Glen Ellyn. Day length and temperatures influence monarchs to move.
Fourth generation monarchs are born in September and October and are biologically different from previous generations. They live longer (8-9 months) and do not mate or lay eggs until the following spring after they fly north and reach areas with milkweed. Their offspring and successive generations, which generally live only 2 to 5 weeks, continue the trip further north until monarchs populate virtually the entire eastern U.S. by June or July.
Fourth generation monarch butterflies feed on late blooming flowers like goldenrod and aster. As they head south, they’ll find more food and will actually gain weight during migration, Touzalin said. Usually animals lose weight during migration because they use so much energy and deplete their fat stores.
Using a mouthpart called a proboscis, adult monarch butterflies can feed on nectar from a wide variety of flowers. But monarchs will only lay their eggs on milkweed because that’s the only food the caterpillars will eat. Milkweed contains toxic steroids in its leaves to give caterpillars and monarch butterflies some protection from predators.
Fall is a great time to plant milkweed by seed in your yard because it needs cold weather to stratify before emerging in the spring. Milkweed varieties native to DuPage include common, swamp or rose, prairie, poke, tall green, whorled and butterfly weed. Pick up a pollinator seed packet at the District’s headquarters in Danada Forest Preserve, and plant it in your yard to help pollinators like monarch butterflies.
The Forest Preserve District has stepped up its longstanding support of monarchs and other pollinators. Milkweed grows on about 30 percent of forest preserve land, and since 2010 habitat restoration projects at 11 different sites have bumped up that number by using over 50 seed mixes that include milkweeds native to DuPage.
The District’s Willowbrook Wildlife Center is a designated “Monarch Waystation,” which means it provides resources necessary for monarchs to produce successive generations and sustain their migration.