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Insects below zero

Monarch butterflies in Mexico
Credit: Flickr (Pablo Leautaud)
Monarch butterflies in Mexico
Insects below zero

Flowers to gather nectar from, leaves to munch on, heat to get active with – summer is insect season! But what happens when the mercury drops below zero? Here are some astonishing adaptations developed by insects to meet the challenge of winter.

Diapause

A long “pause” until the nice weather comes back is the strategy adapted by the majority of our insects. To get through the cold season, they stop moving, stop eating, and slow their metabolisms to a minimum, halting their growth and other activity. Diapause allows insects to reduce their energy needs until such time as nature becomes generous again.

With the end of summer approaching, the diapause period has to be prepared for. As the days get shorter and shorter, the insects become aware that it’s time to accumulate reserves of fat, an energy source. Then, as autumn approaches, they go off in search of comfortable shelter where they can spend the difficult months ahead. The Mourning Cloak butterfly, for example, elects to insinuate itself under the bark of a tree. Other insects hide their eggs in the ground or under dead tree trunks, where they’ll spend the winter. But as effective as they are at keeping insects from being noticed, these hiding places aren’t enough to prevent them from freezing. So insects have to produce an antifreeze, which prevents ice crystals from destroying their cells. And now they’re ready to patiently await the arrival of spring.

Migration

Like some other butterflies, the monarch adopts the strategy of flight. In what is a true exploit among migrants, it travels close to 4,000 kilometers to get to Mexico’s Sierra Madre mountains. To make it from one end to the other of this vast territory, it has to fill up on nectar the entire length of the trip. And what is surprising is that, to avoid any loss of energy at this crucial stage, the migrating generation of monarchs does not complete the development of its reproductive system. For that to happen, warm weather will have to return. Meanwhile, the monarchs remain almost immobile, suspended in clusters from the branches of the sacred fir, waiting for renewal.

Activity

Snow flies are one of the rare insects that carry on being active during the winter. Their strategy? Not having to feed themselves, soaking their muscles and other tissues in an effective antifreeze, and moving about on tough legs adapted to the snow. Since energy is at a premium, males and females waste no time with preliminaries. No sooner do they meet up than mating takes place. Of course, these flies lives in a highly specific micro-habitat. There, under the cover of snow, they find milder, more consistent temperatures.

The ability of insects to adapt to winter is quit simply astounding!

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