Freezing temperatures and butterflies

Now that much of the US has already experienced freezing temperatures, butterflies and moths in those areas are set for the winter. Those that overwinter have gone into diapause. Those that migrate south have migrated. Those that will die in the cold have done so.

So where are they? Let’s look!

Some species, such as Mourning Cloaks and Question Marks stay where they are (as adult butterflies) during the winter. Hiding in cracks and crevices in wood, they come out only on the warmest days, if at all.

Some are young caterpillars, simply tucked away in sewed-together leaves. Having produced sorbitol and glycerol in their hemolymph/blood, they can withstand freezing temperatures for days to months without a break.

A Viceroy caterpillar hides in a rolled leaf for the winter. The caterpillar is totally hidden.

Tawny Emperor caterpillars hide inside leaves during the winter.

Some species, such as the Striped Hairstreak, spend the winter in their eggs. In the spring, the eggs hatch and the young caterpillar begins eating fresh tender leaves.

Striped Hairstreak butterflies spend the winter as eggs. All other stages die before winter or in the cold that winter brings.

Swallowtails and a few other species spend the winter in chrysalis. Whether in a milder winter in Florida or months of ice and snow in Canada and the northern US, the chrysalis can survive sub-zero temperatures. In the spring, the adult butterfly emerges, mates, and begins laying eggs on fresh tender spring leaves.

Eastern Tiger Swallowtail chrysalis on a stem.

Gulf Fritillary butterflies fly south and spend the winter in warmer areas, where day temperatures stay above 60 degrees.

Monarch butterflies in Mexico, where they spend the winter in the mountains where temperature are cool. — Monarch butterflies in Mexico, where they spend the winter in the mountains where temperature are cool but do not stay below freezing.

So while we go about our business in cold temperatures, wearing heavy coats and turning on heaters, butterflies have either flown south or are waiting out the cold, patiently waiting until spring when longer days and warmer temperatures trigger them to come out of diapause and begin active living again.