It seems almost unbelievable on a frigid winter’s day, but some butterflies in central PA endure the winter as adults. The mourning cloak butterfly (Nymphalis antiopa) tucks itself away in crevices, underneath loose tree bark, or even in unheated buildings. For this reason, it is one of the earliest butterflies seen in the spring—and may even be spotted flying during warm spells in January or February. (This allows the mourning cloak to be first in line at the buffet of its favorite food—tree sap—as it begins its seasonal rise.) 

Besides the excellent camouflage provided by its underwings, this butterfly has other winter strategies. It avoids freezing by manufacturing cryoprotectants, chemical compounds which supercool its bodily fluids and tissues. Its dark wings act as solar panels on sunny days, efficiently soaking up warmth. And its unusually hairy body provides extra insulation from the cold.

As if you needed yet another good reason to add an oak tree or two to your pollinator garden, the mourning cloak provides it: Oak sap is a particular favorite!