House spiders, such as the common American House Spider (Parasteatoda tepidariorum) or the long-bodied cellar spider (Pholcus phalangioides), shift their behavior indoors when cold weather arrives. While the surge of outdoor insects vanishes during the winter, the stable environment of a human dwelling provides a year-round source of prey and shelter for these arachnids. This steady, controlled indoor climate allows them to remain active or semi-active, unlike their outdoor counterparts which must enter deep dormancy.
How House Spiders Survive Winter Scarcity
House spiders are ectothermic, meaning they rely on the external environment to regulate their body temperature. This cold-blooded nature is an advantage during scarcity, as lower indoor temperatures naturally slow down their bodily functions. They conserve energy by entering a state of reduced activity known as diapause, which is similar to hibernation but not as deep. Their metabolism can be naturally lower than other invertebrates of a similar size, sometimes by as much as 50 percent. They seek out protected microclimates within the house, such as wall voids, under furniture, or in basements, where temperatures are stable and above freezing.
The Primary Indoor Winter Diet
Most homes maintain a small population of arthropods that serve as a consistent food source for house spiders during the winter months. These prey items are often pests that have also sought refuge indoors or breed continuously in micro-habitats throughout the structure. Small, residual flies are a common winter meal, including fungus gnats that breed in houseplant soil and fruit flies attracted to kitchen areas. House spiders also prey upon various pantry pests, such as Indian meal moths and flour beetles, which infest stored dry goods in kitchens and pantries. Other non-flying arthropods, such as silverfish and booklice, are common targets in damp areas like basements and bathrooms, and spiders will actively hunt or trap these slow-moving creatures.
Hydration and Alternative Feeding
While house spiders can endure long periods without food, hydration is often a more pressing concern, especially in the dry air of heated homes. Spiders primarily obtain moisture from the bodily fluids of the prey they consume. When food is scarce, they must rely on environmental sources to meet their water needs. Condensation is a major source of water, with spiders frequently drinking tiny droplets that form on windowsills, pipes, or their own silk webs in humid areas like bathrooms. Spiders will occasionally resort to scavenging dead insects or the remnants of larger dead arthropods. A final, rare survival tactic is cannibalism, where a spider consumes a smaller or weaker member of its own species when starvation is imminent.