Many people encounter spiders indoors and wonder if these arachnids could survive outside. This common question stems from curiosity about their preferred environments. Understanding the specific adaptations of “house spiders” clarifies their relationship with human dwellings.
What Defines a “House” Spider?
A “house spider” refers to species that have successfully adapted to living alongside humans, often spending their entire lives indoors. Common examples include the common house spider (Parasteatoda tepidariorum) and the barn funnel weaver (Tegenaria domestica). While sometimes found outdoors in sheltered locations, these species have evolved to thrive in the consistent conditions within buildings. They were often introduced globally through human activity and have since flourished in these artificial habitats.
These spiders construct characteristic webs, such as the irregular “cobwebs” of Parasteatoda tepidariorum or the sheet-like webs with a funnel-shaped retreat made by Tegenaria domestica. Their adaptations make them well-suited for stable indoor environments, mimicking ancestral habitats like caves or hollow trees. They typically prefer quiet, undisturbed areas within a home, such as corners, basements, attics, or behind furniture.
Challenges of Outdoor Survival
Releasing a house spider outdoors often leads to its demise, as most species are not equipped for the variable external environment. House spiders are ectothermic, relying on their surroundings to regulate body temperature. They prefer a stable range, typically 18°C to 29°C (65°F to 85°F). Outdoors, they face extreme temperature fluctuations, from freezing cold to intense heat, which significantly impacts their activity and survival. Unlike some outdoor species, house spiders generally lack natural antifreezes to survive cold.
Variable humidity levels also pose a significant challenge, as house spiders require specific moisture for hydration and successful molting. Indoor environments provide stable humidity (around 40-60% relative humidity) conducive to their life cycle, whereas outdoors, conditions can be excessively dry or wet. Beyond environmental factors, house spiders face increased predation from diverse animals, including birds, lizards, and various insects. Exposure to strong winds and heavy rain further threatens their delicate webs and bodies.
Factors Driving Them Indoors
Human homes are particularly appealing to house spiders due to the stable conditions they offer. Consistent indoor temperatures and humidity levels provide a predictable environment, which is highly beneficial for these arachnids.
The abundance of food sources also acts as a strong attractant. Homes often harbor various insects such as flies, mosquitoes, ants, and mites, which serve as prey for house spiders. Additionally, human dwellings provide numerous hiding spots and safe places for web-building and reproduction. These undisturbed corners and crevices allow spiders to establish their webs and lay egg sacs. While some spiders might enter a home accidentally, the favorable conditions often lead them to stay and establish a permanent presence.