What happens to butterflies in winter? These seemingly delicate, ephemeral creatures have devised several strategies for surviving during the long, cold months of an Illinois winter.
The angular, multi-hued leaves, blown about by the cool winds of late autumn, may remind us of the recent past, of the colorful butterflies sailing across the spring and summer landscape, propelled by gentler warmer winds.
With the advent of shorter days and cooler temperatures, though, these ephemeral spectors of warmer times vanish.
Clues to their apparent magical disppearance, however, can be found in the massing together of monarchs on clear fall days, in the presence of partially to fully mature caterpillars on dying foodplants, or in the sudden appearance of a tattered butterfly on a warm, sunny day in January.
Certainly the most straightforward method to deal with winter is to head south.
Only a single Illinois species employs this tactic—the familiar monarch.
Illinois monarchs group together each fall and head south for central Mexico to spend the winter. These migrants are not the ones that came north the previous year, but their children and grandchildren. Most make it through the winter and head north in spring, laying eggs as they go. Some make it all the way north to Illinois to lay eggs for the new crop of fall migrants, others do not, and it is these succeeding generations that complete this remarkable journey.
Caterpillars that are full grown in late summer or early fall will likely spend the winter in a leaf-brown chrysalis—attached to the stem of its last meal—to emerge with the warmth of spring, replete with an unblemished scaly covering.
Employing yet another strategy, the viceroy spends the winter as a partially grown larvae, rolled up in a leaf attached to its foodplant.
Other butterflies spend the winter as adults, usually hidden under loose bark or in any appropriate crack and crevice. These individuals are not true hibernators as they will rouse on warm winter days.
It's not too unusual to see a battered mourning cloak flitting about in the weak winter sun, a premonition of things to come.