The beautiful monarch butterfly (Danaus plexippus), with its bold orange and black wings, is found in our area from late May through November. Those seen early in the summer have arrived from south of us, where they were born. The arriving females lay their eggs here on milkweed plants where the hatching caterpillars grow fat on the leaves. The toxic chemicals from the milkweed plant accumulate in the caterpillars’ bodies, making them distasteful to would-be predators, such as birds. These toxins remain as the caterpillars metamorphose into adult butterflies. The adult’s orange and black coloration is a warning to predators that it is not a tasty meal.
Amazingly, the butterflies that emerge here in late summer will survive the winter by migrating thousands of miles to southern Mexico. There, they will overwinter by the millions at specific roosting sites of only twenty to thirty acres in size. (Though the Mexican government protects these sites, deforestation continues in the area.) In the spring they will journey north again to lay eggs in Texas and other southern states. Having passed on the torch to the next generation, the winter monarchs will die.
The monarchs that reach Connecticut in early summer are the children or grandchildren of the overwintering population in Mexico. Each successive generation heads further north, following the vital nectar sources of native flowers and cultivated gardens, which are in full swing at the time. Goldenrod, coneflower, milkweeds (including butterfly weed) and butterfly bush are but a few of the nectar sources attractive to monarchs.
This year’s last generation of monarchs is getting ready for its long trip south. But their parents have since died and there is no one to show them the way. Studies have found that a monarch navigates by an internal clock; the butterfly’s exposure to the sun while it is a caterpillar and then an adult sets the clock.
The Connecticut Butterfly Association and Menunkatuck participate in a monarch tagging program sponsored by Monarch Watch. (The tagging of individual monarchs helps us to better understand their migration routes and how to protect them.) Hammonasset is a great place to see migrating monarchs, as it is a coastal site with plenty of nectar sources (in its butterfly garden and surrounding natural areas). The public is invited to participate in both of these tagging events. Bring a butterfly net and help catch the monarchs for tagging, or simply come to observe these majestic insects up close.