In summer, insects are everywhere. You see butterflies and bees floating along the flowers, flies and mosquitoes buzzing around endlessly, ants marching, grasshoppers hopping and crickets chirping.
But once the temperatures drop and winter comes, these bugs start to disappear. They — or their descendants — somehow manage to survive the cold because they resurface again when the weather warms up.
"They're pragmatists and the negative pressures of evolution have conferred strategies on how to get through the winter," Dr. Gale E. Ridge, associate scientist at the Connecticut Agricultural Experiment Station, tells MNN.
Some commute or find places to hide, while others change their body chemistry or just leave the world for future generations. Despite these creative solutions, climate change is having an impact on how insects survive the winter, Ridge says.
"Climate change is unpopping the cork and lengthening the seasons. Warmer, milder winters [lead to] extra generations with overwintering insects more likely to survive because of the milder weather."
Here's a look at some of the unusual survival strategies insects use to combat winter weather.
If it's too cold where they are, some insects migrate to warmer places. The most well-known example is the monarch butterfly, which travels thousands of miles with millions of its closest friends to escape cold temperatures. Monarch butterflies in the eastern U.S. and Canada fly 2,000 miles or more to spend their winters in California or Mexico.
"Insects surf air currents to cover great distances," Ridge says. "Pilots call them air plankton. In summer alone, there are 17 species of insects passing over your head at any given time."
When cold weather hits, some insects enter diapause — a kind of dormant state where all their growth and activities are put on hold in a semi-frozen condition. It's similar to the hibernation experienced by many warm-blooded animals. Diapause is usually triggered by the shorter days leading up to winter, says Smithsonian, not the actual cold weather.
The invasive emerald ash borer, an invasive insect that kills ash trees, enters diapause in the winter. In this dormant state, "they don't do anything," Brent Sinclair, the director of the Insect Low Temperature Biology Lab at the University of Western Ontario, tells Business Insider. "They don't develop. They just sit under the bark of trees where they've been feeding all summer."
The Arctic woolly bear moth caterpillar can survive extreme temperatures. (Photo: Mike Beauregard [CC BY 2.0]/Flickr)
Some insects produce their own type of antifreeze to survive freezing temperatures while in a diapause state. When temperatures start to get colder in fall and winter, many insects make cryoprotectants — compounds including glycerol and sorbitol — that keep their bodies from forming deadly ice crystals, writes master gardener Rita Potter in the York Daily Record. This homemade antifreeze allows insects to survive even when temperatures fall below freezing. Woolly bear caterpillars use this method to make it through the winter by curling up in leaf litter. So does the Alaska Upis beetle, which can withstand temperatures reaching down to a chilling minus 100 degrees F, reports Smithsonian.
Technically, some insects don't survive the winter at all. But before they die, they lay eggs that will hatch in the spring.
"One of the most common ways that bugs deal with winter, especially in North America, is that they are seasonal," scientist Kristie Reddick tells The Washington Post. Crickets, praying mantises, grasshoppers and katydids all leave their eggs behind so new insects can emerge in the spring.
Spiders — which technically are arachnids, not insects — also do this, says Ridge. Females lay their egg sacs in the fall, then die. Then the spiderlings are born in the spring once the cold weather has passed.
When winter comes, some bugs avoid freezing by snuggling to stay warm. Honeybees huddle together in their hives, using their collective body heat to keep each other warm. "They perform the equivalent of shivering to create heat so they can create a microradiator in the colony so they stay warm and fend off the cold," says Ridge.
Similarly, ants and termites stick together, going a litter farther underground, according to Thought Co. They go below the frost line where there's warmth from all those insect bodies. Convergent lady beetles also gather in large groups on rocks or on branches to stay warm.
Some insects survive the winter simply by seeking out warm spots to hide. Cockroaches, ever the opportunists, will seek warmth if you give them an opening.
Insects like the multicolored Asian lady beetle, brown marmorated stink bug and western conifer seed bug will wait out the winter in warm, dry buildings. "Adults will emerge in the late summer and will just go and hide in sheltered locations," says Ridge. Their cues to go into hiding are shorter days and colder temperatures. They'll stay inside until warmer, longer days are back.