Did you know that some of our moths and butterflies spend the winter as winged adults? Moths and butterflies, known as lepidopterans, are members of the insect order. They exhibit complete metamorphism, meaning their larval form (in this case, known as caterpillars) is totally different from the adult form. This differs from incomplete metamorphism exhibited by more primitive insects (like crickets and grasshoppers), where the adults look the same as the larval form (in this case, known as nymphs), only larger and with wings. Lepidopterans can over-winter as eggs, larvae, pupae, or adults, depending on the species. While most species of both moths and butterflies over-winter as pupae in silk-wrapped cocoons (moths) or secreted shells, called chrysalis (butterflies), three butterflies can be found throughout the winter as adults. In March and early April, Mourning Cloak, Question Mark and Comma butterflies can be seen flying in the leafless forest searching for mates. These members of the brush-footed butterfly family survive the winter by drastically lowering their metabolism, producing glycols (an antifreeze substance in the blood), and supercooling the water in their cells (allowing the water to drop below the freezing point and still remain a liquid). While most of the winter, these butterflies will remain dormant, they can occasionally be seen in flight during late winter warm spells.

Surprisingly, there are about fifty species of North American moths that not only over-winter as adults, but are active during warm spells throughout the winter. What is more surprising, is that some moth species of the Geometrid family can fly at temperatures as low as 26° F, yet they cannot generate heat, shiver, produce glycols, or even supercool! Science does not yet know how they do it. They apparently feed exclusively on sweet sap oozing from wounds in tree branches made by squirrels for fuel. This is the time to find these unique moths by scraping honey, molasses, and mashed fruit on tree bark and checking them after dark. By the end of April, these moths will have mated, laid eggs, enabled the eggs to hatch into caterpillars eating the newly emerging foliage and then drop into the leaf litter to form it’s cocoon, remaining dormant throughout the summer (aestivating -- the opposite of hibernating), until time for the fall metamorphosis.

While evolutionary relationships among major Lepidopteran groups (moths and butterflies) are not well understood, due to the paucity of fossils, current theory suggests that butterflies are just a branch of brightly colored moths. It is believed that the first lepidopterans were moths that evolved with flowering plants during the Cretaceous Period, often called the "Age of Flowering Plants," 65 million to 135 million years ago -- a time when dinosaurs also roamed the earth. Early in their evolutionary history, moths probably escaped most bird predation by becoming nocturnal. But by the Eocene, some 45 million years ago, echolocating bats evolved, and moths were again vulnerable at night. In response, some moth species evolved ear structures that allowed them to hear the bat’s sonar. In a typical tit-for-tat fashion, bats then evolved a higher frequency pitch that could not be heard by moths. At present, the ball is again in the moth’s court. Butterflies, on the other hand, originally all nocturnal fliers, opted to return to a diurnal existence. (Again, the exception to the case exists with a nocturnal group of butterflies known in Panama. Not surprisingly, these butterflies have an unusual ear, found on its wings, capable of hearing ultrasound!)

There are roughly ten times more species of moths than butterflies. Comparing species of moths to butterflies respectively, there are 100, 000 versus 15-20,000 species worldwide; 11,000 versus 750 in North America, and 1,000 versus 150 species found in Maryland.