How Insects Survive Winter
It’s pretty official, bugs are weird creatures. If you have ever taken the time to study a walking stick crawl across the limb of a tree, or watch a summer night light up from fireflies, you’ve noticed how strange and alien most bugs can appear. However, some of the weirdest parts of pests come from the things you can’t see. So while us Texans survive “winter” by bundling up with layers and sitting by fires, the survival of insects is probably the last thing on our minds. Most of us probably just think, “Awesome, they’re dead.” Just know some insects survive winter by becoming even weirder when the weather gets cooler.
As humans, we’re warm-blooded creatures, which means our bodies remain at a constant temperature despite external temperatures changes. Now imagine that wasn’t the case, and you’re stuck trudging through a snowstorm without a jacket. If you were an aphid, you wouldn’t be too concerned, you’d just convert your body fluids into anti-freeze, no big deal. If you were a cockroach, you’d survive by allowing some ice to form in your body, but just the right amount to keep from dying. That’s right, some insects actually change their internal biochemistry to withstand cold temperatures. But the diversity of insects is far too great for them all to survive winter the same way.
Freeze-avoidance vs. Freeze-tolerance
As previously mentioned, some insects are freeze-avoidant, meaning while they CAN freeze, their internal biochemistry avoids the process by converting their internal body fluids into cryoprotectants, aka, anti-freeze. Cryoprotectants, such as glycerol and mannitol are used to disrupt the formation of ice crystals in the insect’s body, thus allowing the insect to avoid freezing unless the temperature reaches below the freezing point of the cryoprotectant itself. The cryoprotectant, glycerol, is the most common found in freeze-avoidant insects and is evenly distributed throughout each part of the insect’s body. Examples of freeze-avoidant insects include ticks, aphids, and certain species of beetles. Many freeze-avoidant insects tend to live and feed primarily in trees and are generally found in the Northern Hemisphere.
Freeze-tolerant insects on the other hand, actually allow ice crystals to form in their bodies but control the freezing process by only allowing ice to form in extracellular spaces. Ice formation in intracellular spaces is generally lethal. As long as freeze-tolerant insects keep their intracellular spaces from forming ice crystals, they can survive with up to 65% of their bodies being frozen! Some of these freeze-tolerant insects still produce cryoprotectant chemicals, controlling the rate at which their bodies freeze, and where the freezing occurs. However, the amount of cryoprotectant found in freeze-tolerant insects is much lower than the amount found in freeze-avoidant insects. Freeze-tolerant insects also start to freeze their bodies at much higher temperatures, moderating how much ice is formed in their bodies and slowly adjusting for further ice crystal formation as the temperature drops. Insects that use these methods include cockroaches and some caterpillars.
Most freeze-tolerant species of insects are found in the Southern Hemisphere where the weather fluctuates at a greater rate, allowing them to survive both sudden cold fronts and warmer temperatures. As mentioned above, freeze-avoidant insects are generally found in the Northern Hemisphere where winters are more consistently below freezing, and producing an internal anti-freeze is a better method for surviving longer stints in the cold.
There are also insects that survive winter in more traditional ways. Some burrow underneath rocks, woodpiles, and soil to wait out the cold months, while others bury their eggs to continue on the species while they perish in the cold. Migrating insects such as butterflies flee the cold, mate, and die while their offspring return north the next spring. Others, as we all well know, like to hang out with us by the fireplace. Even freeze-tolerant insects like cockroaches will forego their biological marvels to hang out in our cupboards. That’s why it’s best to maintain your pest control services throughout the winter months, even when it seems like there are no pests to be controlled! As the winter storm of 2021 took many Texas residents by surprise, it’s no question that the local insect population felt the same way, and likely found their way inside houses to survive.
As those of us in Central Texas bunker down to survive another frigid February, insects are doing the same thing outside in fantastical ways. Nevertheless, these marvelous insects will quickly turn to your home if the temperature becomes too extreme even for their bodies to handle. If you are looking to keep your home from becoming a pest-filled hovel this winter, make sure to continue your regularly scheduled pest control visits with the Bug-A-Meister.
