As the year goes by and we feel the weather shifting towards winter, we find more and more insects in our homes. By and large, these insects are trying to get out of the cold, and find our homes just as good an answer as cracks in treestumps, downed wood, or burrows beneath the frostline.
There are two main types of animal adaptation to cold. Freeze-Tolerance and Freeze-Avoidance.
Freeze-Tolerant organisms can survive their bodies being frozen – they’ll thaw and wake up in the spring, none the worse for wear. Perhaps with a bit of amnesia, but physically unharmed. Many woodboring lumber pest species do this, as do some frogs (e.g. our Columbia Spotted Frog). Their trick is that they expel most of the water from their body before freezing (i.e. empty out their digestive tract) so that they have as little ice forming inside their body as possible. Additionally, they make special “ice-nucleating agents” that help them freeze at higher temperatures. If you have to freeze to survive the winter, it’s best to do so on your own terms.
Freeze-Avoidant (Cold-Tolerant, Freeze-Susceptible) organisms can avoid freezing solid, even when in temperatures far below 32 F. However, if it gets cold enough to freeze them solid, freeze-resistant organisms will die. Stink Bugs and Leaf-Footed Bugs are good examples of this. Many freeze-resistant creatures produce a sugary antifreeze-like compound called “glycerol” in their blood, lowering their freezing point, and thus avoiding freezing. This isn’t just an insect thing – some fish use glycerol, too. Thanks to this adaptation, you can find Leaf-Footed Bugs active in some pretty cold places.
All aquatic insects, as well as fish, are Freeze-Avoidant. This is especially important for aquatic creatures, as contact with ice could otherwise spontaneously freeze them. Some deep-sea arctic fish freeze solid upon contact with ice (link with picture), despite having antifreeze compounds in their blood.
Most of the insects you’ll see invading your homes will be Freeze-Avoidant. Even though they can survive cold temperatures, they’d rather be someplace warmer, someplace with less risk of death.
What insects are beginning to immigrate to your home?