Spiders exhibit distinct temperature preferences that influence their behavior and survival. Unlike mammals, these creatures are ectothermic, meaning their internal body temperature is directly affected by the surrounding environment. This relationship explains why spiders are found in certain habitats and how they adapt to changing conditions.
Spider Temperature Preferences
Spiders generally thrive within a moderate temperature range, avoiding environmental extremes. While preferences vary among the nearly 50,000 known species, most fare best between 70°F and 85°F (21°C and 29°C). Some species, like Eratigena atrica, prefer cooler conditions around 57°F (13.7°C), while others, such as the garden spider Araneus diadematus, favor about 72.5°F (22.5°C). Desert spiders, like Habronattus clypeatus, can endure a broad range, active from 52°F to 133°F (11°C to 56°C), with peak activity between 55°F and 115°F (13°C and 46°C). This diversity reflects their adaptation to specific climatic zones.
All spiders seek stable environments with minimal temperature fluctuations. Their reliance on external heat sources means they must actively position themselves to absorb warmth or find cooler spots. This behavioral thermoregulation is a strategy for maintaining their body temperature within an optimal range, as they adjust their location to gain or lose heat.
How Temperature Affects Spiders
Temperature impacts a spider’s biological processes, including metabolism, activity levels, growth, reproduction, and survival. As ectotherms, their metabolic rate typically increases with rising temperatures, but this relationship has limits.
Excessively high temperatures are detrimental. Above 90°F (32°C), many species become sluggish and seek shelter. Extreme heat, particularly sustained exposure to temperatures reaching 110-120°F (43-49°C), can be lethal due to accelerated fluid loss leading to dehydration and protein denaturation. High temperatures also inhibit growth, resulting in smaller individuals, and negatively affect reproduction, including reduced female fecundity and decreased egg hatching success. Sedentary web-building spiders are susceptible to heat-related mortality as they cannot easily relocate.
Low temperatures also pose challenges. When temperatures fall below their preferred range, a spider’s metabolism slows, impairing movement and hunting. Many species cope with cold by entering diapause, a state of reduced activity and metabolism, to conserve energy. Some spiders possess adaptations, such as natural antifreeze compounds or specialized proteins, which prevent ice crystal formation within their bodily fluids, allowing them to survive temperatures as low as 23°F (-5°C). However, prolonged exposure to severe cold without protective measures, like snow cover, can be fatal.
Why Spiders Seek Shelter
Spiders frequently seek shelter when outdoor temperatures deviate from their preferred range, whether too hot or too cold. This often leads them into human dwellings or other protected spaces offering more stable conditions.
During hot summer months, spiders may enter homes for cooler environments and access to water, which can become scarce outdoors. They find refuge in the consistent indoor temperatures.
As winter approaches and temperatures drop, spiders move indoors to escape the cold. Common indoor hiding spots include basements, attics, wall voids, and other undisturbed, cluttered areas. While some indoor spiders are year-round residents, others may enter through small cracks, gaps around windows and doors, or damaged screens. Their search for shelter is also linked to finding food sources, as other insects, their prey, may also be seeking refuge indoors.