Spiders are cold-blooded, or ectotherms. Their body temperature is regulated by external sources and can vary with the environment without doing them any harm. When cold weather comes spiders that overwinter as adults adapt in several ways. Their metabolism slows down and they become less active. Eventually they become dormant, entering diapause, a hibernation-like state. At the same time, they start producing glycol and protein compounds which act as antifreeze and lower the temperature at which their cells will start freezing. A spider has to get to at least 23 degrees F. to freeze, and sometimes considerably lower.
Where a spider spends the winter depends in large part on the species. Some seek shelter in places where temperatures remain a little warmer than outdoors, such as in leaf litter, rock piles, building cracks and under loose bark. To help block cold wind, some will even build themselves a little pod with their silk, enclosing themselves until it is warm enough to become active again. (Photo: spider in silk pod behind loose bark)
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