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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Two common spiders that we often see carrying their egg sacs are the wolf spider and the nursery web spider. Wolf spiders attach their egg sacs to their spinnerets, whereas nursery web spiders carry them with their mouthparts. When nursery web spiders are about to hatch, the mother puts her egg sac into a silk tent she has spun, and they live there for a week or so. When a wolf spider’s spiderlings emerge from their egg sac, they climb up onto their mother’s abdomen and cling to it while their mother continues to hunt for food. After about a week, when partially grown, the spiderlings disperse, either by ballooning through the air on silk strands or simply by scurrying off along the ground.
All spiders spin silk — some use it to build webs, eggs sacs, draglines, wrap prey and/or disperse in the air. Inside their bodies are glands which produce different types of silk material for different purposes. Liquified silk proteins are pushed out spinnerets, or silk-spinning organs, located at the tip of a spider’s abdomen (most spiders have six). Once the silk solution comes in contact with the air, it solidifies. Each spinneret has a spigot, or nozzle, which controls the consistency of the silk by forming smaller or larger strands. By winding different silk varieties together in varying proportions, spiders can form a wide range of fiber material. Spider silk is extremely strong and flexible. Some varieties are five times as strong as an equal mass of steel and twice as strong as an equal mass of Kevlar.