Monday, February 20, 2017

How Insects Overwinter by Mary Small



Bees Huddling to Keep Warm, photo courtesy CSU Extension

All insects have developed strategies for surviving the winter.  Some migrate to warmer climates, but most stick around.  How do they do it? 

Honeybees really do huddle together…in a ball, with those on the outside of the ball (acting as insulators) gradually exchanging places with the bees on the inside of the ball. The bees on the inside of the ball generate heat through shivering. No helmets or jerseys, though.

Zimmerman Pine Moth Cocoon, photo courtesy CSU Extension
Certain insects overwinter as larvae and either crawl under or into some protective material, like a log, rock, or leaves.  Some of them develop the glycol-like chemicals bodies just like adults. Mountain pine beetle overwinters underneath the bark as larvae that hatched from eggs laid in summer. The poplar twig gall fly overwinters as a maggot and pupates in late winter within its gall. Other insects overwinter as eggs, attached to plants or debris, usually near a source of food to sustain them after they emerge in the spring. Aphids are a good example of this. 

Most of us are familiar with pupae (ie., cocoons),the resting stage of certain insects like butterflies or moths.  The cocoon protects against dehydration and freezing. Southwestern pine tip moths and Zimmerman pine moths overwinter in this way.

Winter conditions can and do kill a lot of insects, especially when there are long periods of cold temperatures with little snow cover. But many survive to begin the cycle again as soon as warmer weather arrives. For more information, see Planttalk Insect Overwintering.