As temperatures drop, many wonder how spiders survive the colder months, especially when their presence indoors seems to increase. Spiders have fascinating adaptations that allow them to endure periods of cold and scarcity.
Dispelling the Hibernation Myth
Spiders do not truly hibernate in the same way mammals like bears do. Hibernation involves a prolonged state of deep dormancy with significant metabolic slowdown, often triggered by food scarcity and cold. Spiders, being cold-blooded creatures, respond to their environment differently. Their internal body temperature is influenced by the surrounding conditions, meaning their activity levels decrease as temperatures fall.
Instead of hibernation, spiders enter a state called “diapause” or simply “overwintering.” Diapause is a period of suspended development or reduced metabolic activity in response to environmental cues such as decreasing temperatures, shorter daylight hours, and reduced food availability. While similar to hibernation in its purpose of energy conservation, spiders in diapause can still be somewhat active and may emerge during warmer spells to seek food. This state allows them to conserve energy and survive until conditions improve.
How Spiders Endure Winter
Spiders have evolved several physiological adaptations to survive cold temperatures. A significant mechanism is the production of “antifreeze” compounds, known as cryoprotectants, in their hemolymph, which is their version of blood. These compounds, such as glycerol, act by lowering the freezing point of their bodily fluids, preventing the formation of ice crystals within their tissues. The presence of these cryoprotectants allows certain spider species to withstand sub-freezing temperatures, sometimes as low as -10°C (14°F).
In addition to cryoprotectants, spiders significantly slow their metabolic rate during colder periods. This reduction conserves energy, enabling them to survive for extended durations without food. Some species can reduce their metabolic rate by as much as 90% during winter.
Some spider species also utilize thermal-hysteresis-factors, proteins that create a difference between the freezing and melting points of their hemolymph, further inhibiting ice formation. Spider eggs, often laid in silken sacs, also receive protection from the cold, with some sacs providing insulation and even incorporating antifreeze proteins.
Where Spiders Go in Colder Months
When winter approaches, spiders seek sheltered locations to escape the harsh conditions. Outdoor spiders often find refuge under bark, within leaf litter, beneath rocks, inside hollow plant stems, or in the top layer of soil, also known as the subnivean zone. These spots offer insulation and protection from extreme cold. Some spiders may even construct small silk pods or “web tents” for additional shelter.
The common belief that spiders flock indoors to escape winter cold is largely a myth. Most spiders found inside homes during winter have likely resided there all year, having been born indoors. Less than 5% of spiders encountered indoors have ever been outside. While some outdoor spiders, like the brown recluse, might occasionally seek warmer indoor spaces, most are not drawn to warm homes. Spiders that do enter homes typically do so through small cracks or openings, seeking undisturbed areas like basements, attics, garages, crawl spaces, or wall voids.