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.

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.

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.

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.