The total time frame for one butterfly’s life cycle (one generation) is about 6-8 weeks, and they go through four stages: egg, caterpillar, chrysalis, butterfly. It grows inside the egg for about 4 days. It then munches milkweed and grows as a monarch caterpillar (larvae) for about 2 more weeks. The caterpillar’s life inside the chrysalis (pupa) lasts about 10 days, and its life as an adult butterfly lasts from 2 to 6 weeks.
The migration of the monarch is unique among butterflies for its distance, with individuals travelling up to 3,000 miles to reach the wintering grounds in the oyamel fir forests of central Mexico. While the northward spring migration is completed by multiple generations following milkweed emergence as the weather warms, the final generation of the year flies the entire way back to Mexico, where their great-great-great grandparents spent the previous winter.
Monarch populations have been declining over the last several years. This decline is due to a combination of factors including: illegal logging and outbreaks of bark beetles on the wintering grounds, winter storms, a loss of breeding habitat, a decline in milkweed, and an increase in pesticide use.
What can you do to help?
Create a welcoming habitat in your yard by planting milkweed for the caterpillars and a variety of nectar plants for the adults. Common and swamp milkweed as well as butterfly weed are all used by monarchs to lay eggs. Good choices for nectar plants, especially for late summer and fall, are goldenrod, asters, ironweed, and joe-pye weed. Several of these plants can be grown in containers, so even those with small spaces can create a butterfly garden. Use pesticides with care and always choose the least-toxic method of pest control.
Monarchs can be tagged, without hurting the butterfly, to help scientists learn more about the dynamics of their annual migration. Tagging efforts can help researchers estimate monarch populations as well as gain critical information on stopover sites that can guide conservation efforts. Each tag is a small, adhesive disk with a unique number that is placed on the underside of the wing. Wissahickon Trails has been tagging monarchs for four years and partners with The Hill at Whitemarsh to raise and tag these important pollinators. We plan to hold a monarch butterfly tagging event for the public this fall--stay tuned.