The animals are getting ready for winter. We often think of birds heading south and resident mammals putting on their winter coats. But what about the insects?
Some insects do migrate southward as winter approaches. Monarch butterflies are a good example. But the insects that stay through our North Dakota winters basically have two options. They must find a way to avoid freezing or tolerate freezing conditions. And it should be no surprise that some have evolved mechanisms to prevent freezing to death at temperatures well below freezing. Some will spend the winter in their larval stage, others as adults, some of which in a hibernation-like state called diapause.
It might surprise you, but it is not so much the cold temperatures that kill insects and other organisms during the winter. It is the formation of ice crystals in their body fluids. Ice crystals can rip and tear cells! Many insects, as well as some other organisms, produce antifreeze-like molecules that lower the freezing point of their body fluids.
These antifreeze-like substances, what biologists call cryoprotectants include ethylene glycol and glycerol, which have been used commercially in automobile anti-freeze. Some insects also produce proteins that function in a similar fashion. Supercooling is also a mechanism that enables insects to tolerate subfreezing temperatures. Body fluids of some insects can be slowly supercooled to at least -40 Fh before ice crystals form.
Bees make it through the winter by clustering together in their hives and generate heat by flexing wing muscles. However, the bees on the outer regions are just clustered together to conserve heat. Occasionally the bees change locations. Some may die, but generally, enough survive to keep he colony viable.
Many of the aquatic insects of course just stay in the water. Others may spend the winter in the bottom sediments where the temperature is a bit above the freezing point. Shallow area, however, are subject to freezing.
So, when you see the signs of the summer insects, such as an old wasp nest, ant hill, plant gall, give some consideration to the adaptations that enable these insects to make it through our North Dakota winters.
