[SciShow intro plays]

Michael: Unlike us lucky endotherms, insects can’t regulate their own body temperatures. They’re at the mercy of their environment. So when the cold winter arrives, how do they keep from freezing? They basically have three choices: They can leave for warmer places, they can wait it out, or they can kick the bucket.

Just like some birds, there are a few insects, like dragonflies or butterflies, fly south for the winter. The most famous of these has got to be the monarch butterfly. There’s a population that normally lives in the northern U.S. and Canada, but spends the winter in the balmy mountain forests of Mexico. Of course, many insects have shorter lives than birds. So, a special migratory generation of the monarchs flies south thousands of miles to Mexico without reproducing, but it takes four or five generations to make the trip back north.

If an insect can’t leave when winter arrives, option number two is to hunker down and wait for things to warm up again. Insects like ladybugs, emerald ash borers, and mourning cloak butterflies burrow into soil or leaf litter for warmth. There, these adult insects enter a kind of hibernation called diapause, thanks to hormones triggered by the shorter days and cooler temperatures of autumn.

Their metabolic rates drop dramatically, so they don’t need as much food. And some species even pump their tissues full of alcohols that act as a natural antifreeze. Basically, these chemicals lower the freezing point inside their cells, which prevents damaging ice crystals from forming.

Now, plenty of insects, like crickets and grasshoppers, just throw in the towel when the temperature drops. The adults die off after reproducing in the fall, and the next generation spends the winter as dormant eggs or larvae. These babies are usually pretty well-equipped for survival: Eggs and larvae can enter diapause just like adults can, and some get extra help from their doomed parents. Praying mantises, for example, envelop their eggs in a foam-like protective protein case.

These days, climate change is messing with the overwintering strategies of some insects. And it’s even letting some less cold-tolerant species venture farther north. Which... usually isn’t so great. Like, thanks to milder winters, the mountain pine beetle has been expanding its range and killing vast swaths of trees in western North America.

So when it gets cold out, do you put on a coat and keep trucking? Curl up under a blanket with hot chocolate until spring? Or do you make like a monarch and head for the tropics? Whatever your way of dealing, spare a thought for the insects that make it work without central heating – just with some clever adaptations.

Thanks to Patreon patron Zach Lerman for asking, and thanks to all of our patrons who keep these answers coming. If you’d like to submit questions to be answered, go to Patreon.com/SciShow. And don’t forget to go to YouTube.com/SciShow and subscribe!