Where do butterflies go in the winter? Do all butterflies die? Do all butterflies fly south?
The answer is simple: it depends upon the species of butterfly about which you are asking. Some enter diapause, freeze, and live through temperatures well below 32 degrees F.
Each species that enters diapause will do so in a different life stage; egg, larva, pupa, or adult. These species spend the winter as caterpillars.
Tawny Emperor, Hackberry Emperor, Viceroy, Red-spotted Purple, and many other species spend the winter as larvae. They create a nest out of leaves and wait until spring to emerge. These nests are called hibernacula (singular = hibernaculum). When spring arrives with longer days and new leaves on their trees, they emerge and begin eating and growing again.
In the winter, these trees will drop their leaves. Caterpillars that overwinter will instinctively first sew their chosen leaves to the twig. Some species simply sew several leaves together or fold one leaf and stay inside during the winter. Some species, such as Tawny Emperors, will change color from green to brown inside their hibernaculum. Brown caterpillars inside brown leaves would be extremely difficult to see.
Viceroy and Red-spotted Purple caterpillars cut a leaf to a specific shape after sewing it to the twig. They then lay a layer of silk over the leaf. As the silk dries, it draws the sides of the leaf into a tight roll. The caterpillars stay inside the leaf roll during the winter.
Swallowtail butterflies spend the winter as chrysalides. Just before they pupate, the longer nights and cooler temperatures will trigger the caterpillar to become a chrysalis and wait until spring to emerge.
Other species spend the winter as adults. Monarch butterflies migrate to warmer climates or to overwintering sites only to begin their return flight again in the spring. Many species migrate to warmer climates for the winter and continue pairing and laying eggs, a normal lifecycle, during the winter. Their offspring migrate back in the spring.
Other species will remain all winter. Mourning Cloak butterflies will hide in cracks in wood, trees, wood piles, and other places during the winter. They may be covered with snow for a long duration. In the spring, they become active, pairing and laying eggs again.
When you are cleaning up your garden in late fall, preparing for the winter, use caution! When you trim branches and tidy up, set the branches and leaves aside in case there are caterpillars or chrysalides hiding on them. In the spring, after they have had time to emerge, you can compost or otherwise dispose of the material without harming butterflies.