How Do Insects Survive the Cold Northern Winter?
I found this female Ichneumon wasp (Ichneumon centrator) while cutting sugar maple logs for cordwood. The adult females survive the cold of winter by hiding beneath loose bark of fallen trees.
This larva of a Fire-Colored Beetle (Dendroides canadensis) seen below was also found under the loose bark of a dead sugar maple log. Like the ichneumon wasp above, it is also ready to spend the cold winter months under bark.
And the carpenter ants in the photo below (Camponotus pennsylvanicus) were also found under the bark of a dead tree, this time an Eastern Hemlock log. Most insects use a strategy to survive the cold winter months called Diapause.
For many insects their “long winter’s nap” is called Diapause, a period of suspended development and slowed metabolism. This is the most common overwintering mode for insects according to Leather et al. 1993. This period is marked with a preparatory time followed with a time when the insect does not feed. In the course of an insect life, it typically will enter diapause as it progresses from egg to adult. The life form — egg, larva, pupa, or adult – the insect overwinters in depends on the particular species. This is true of insects in both warm and cold climates.
But how do Insects tolerate the cold northern winters?
Insects have different strategies of cold hardiness that allow them to survive at low temperatures. While some can tolerate freezing, most insects in our climate use the biochemical strategy of supercooling or freeze avoidance and many of them overwinter in an immobile state as larvae or pupae (Leather et al. 1992).
Supercooling is when water cools below the freezing point yet does not freeze. This process is initiated in the fall. The insect stops feeding and clears the digestive system, this removes water and naturally increases solubles. Next an increase in polyols (an alcohol) and sugars occur (glycerol is the most common sugar) which act like antifreeze and are collectively known as cryoprotectants. Overwintering larvae can supercool to temps ranging from -68F to -86F! They remain in this state of dormancy until the warmer temperatures of spring arrive.
