When most people think about hibernation, they picture bears snoozing away the cold winter in their dens. You’re right that other animals do that, too.
I talked about your question with my friend Laurel Hansen. She’s an entomology professor at Washington State University. Her specialty is carpenter ants.
“We think most ants in our temperate climate will have diapausing larvae and what I would call overwintering adults,” Hansen said.
Diapausing and overwintering are like hibernating but not quite the same. There are a few things to know about ants to understand what these terms mean.
First, ants are social insects. An ant colony works together so closely that scientists think of them as a single unit—called a superorganism.
Second, ants undergo complete metamorphosis. That means they go through four life stages: egg, larva, pupa and adult.
After they hatch from eggs, juvenile ants are called larvae—or larva for just one. They look like small, white worms. Worker ants feed the larvae in the nest. The larvae spend their time eating and growing. As they get bigger, they molt. They shed their old body covering—called an exoskeleton—and secrete a new one.
These ants are called pupae when they are in the process of changing into adults. Some ant pupae do this inside a cocoon. Others just curl up. They slowly get darker as they change into adults.
Scientists recently learned that ant pupae do something amazing. They leak a nutritious liquid. It’s good for the whole colony—especially the youngest larvae. Workers will even hold up larvae so they can drink this “ant milk” from the pupae.
Ant colonies last for many years. They need strategies to survive cold winters without food. What they do depends on the ant’s life stage.
Larvae diapause through winter. That means they stop developing. They don’t eat or move. It’s like they pressed pause until winter ends. Once spring arrives, they become pupae.
Adults do something more like hibernation. Just like bears, ants build their fat stores before winter. That’s the fuel they’ll use to stay alive. They save energy by slowing their body systems way down. They also make a chemical that works like antifreeze. It keeps the insides of their bodies juicy and free of ice crystals.
“For adults, it’s not a true diapause, and it’s not a true hibernation,” Hansen said. “If you crack open a nest in the winter, the ants will be moving. But they’re slower, and their respiration is about half of what it will be in the summer.”
You might notice ants in your home in spring, especially in the kitchen and bathroom. Those ants are leaving their nests after a long winter’s rest. They’re probably looking for water. They’ll take it back to the nest to make it humid and cozy for their colony.
Just like budding trees and blooming flowers, seeing ants out and about is a sign that spring is around the corner.