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Eastham, MA 02642

A Good Year for Monarchs in the Northeast

It was a good year for monarch butterflies in the Northeast this year. Many of our members reported almost daily visitation of the monarchs in their butterfly gardens. There was a lot of egg-laying on milkweed plants resulting in the emergence of tiny caterpillars in 3-4 days. The caterpillars feast on the milkweed leaves and grow to about 3” before they leave the milkweed plant to pupate into a chrysalis. The metamorphosis process, which lasts 10-12 days, transforms the former caterpillar into the beautiful butterfly. The monarchs that emerge in late summer in our region are mostly the fourth generation of their great, great grandparents that left the Mexico overwintering sites in February. Although they look the same, this generation is special. The shorter days and cooler temperatures result in changes that make them non-reproductive and extend their life span to many months, since they need to make the long migration back to Mexico to overwinter until the return migration starts again next spring.

This year demonstrated the importance of our butterfly gardens to the reproduction and survival of not only monarchs but all butterflies. In one of our gardens, we conducted an experiment to determine which species of milkweed they prefer for reproduction. There are three kinds of milkweed in the Northeast: common, swamp, and butterfly weed. The most egg laying and caterpillar feeding occurred on the swamp milkweed, followed distantly by butterfly weed. There was no egg laying or caterpillars on the common milkweed. This is good news for the home gardener since these species are the most beautiful in bloom and easiest to control, propagating only by seed. Even just a few plants in a garden can make a difference and both are available at local nurseries.