On a warm afternoon in late February, I was checking for the first emergence of woodland wildflowers in Bill's Woods. Suddenly a beautiful velvety-purple butterfly with wings bordered by what looked like cream-colored lace flew by. It was my first butterfly of the year -- a Mourning Cloak. It landed on the trunk of a partially sunlit tree and drank sap for a minute or two at a small hole made by a woodpecker sometime earlier in the day.
Adult Hibernators
Where did these early butterflies come from, when they were absent the day before? What would they do when the weather again froze the tree sap? And why is the Mourning Cloak almost always one of the first butterflies to be seen each spring?
The Mourning Cloak is one of the Anglewing-Tortoiseshell group of butterflies present in the Campus Natural Areas. Others include the Question Mark, Eastern Comma, Red Admiral, and Milbert's and Compton 's Tortoiseshells. Butterflies of this group are among the first to be seen each year, in part because they overwinter as adults. They shelter in small cracks in trees and buildings, emerging on warm days to fly and to feed. Most are found in and at the edges of woodlands. They differ from many other butterflies by feeding on tree and shrub sap and fruit rather than flower nectar. Some eat mammal scat and carrion as well.
Although Mourning Cloak adults drink sap, their larvae require leaves of black cherry and other trees and shrubs. Milbert's Tortoiseshell and Red Admiral larvae eat nettle. All these butterflies are able to begin breeding early, since they start the year as adults and do not depend on nectar for their food. Some of them breed in early spring, aestivate (go through a period of dormancy in the summer) and reappear in fall.
Larval Hibernators
By late April, spectacular black-striped, bright yellow Eastern Tiger Swallowtails appear, often flying high in the tree canopy or along the edges of woodlands. These butterflies, like many others, hibernate in the larval stage. Their larvae feed on the leaves of black cherries, ash, basswood and other deciduous woodland trees.
Long-distance Migrants
The familiar black-striped orange Monarch butterflies usually do not appear in Madison until late May. Most of the Monarchs we see here, nectaring on flowers and laying eggs on milkweeds, are not the same individuals that wintered in the forests of Mexico . They are new adults that hatched and metamorphosed in the southern United States . Before we see large numbers of Monarchs in Madison , a whole generation must live to adulthood and migrate north.
Wintering in Egg Stage
Many, though not all, of the late spring and summer butterflies of gardens, prairies, and fields have overwintered in the egg stage. Most adults require nectar from flowers.
Butterflies of the CNA
Many different butterflies can be found in the CNA (see our website for a list and photos). Each species has its particular season of flight, habits and habitat needs. Watch to see where each feeds and lays eggs.
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