House spiders are common residents in human dwellings worldwide. Their presence often sparks curiosity and apprehension for many homeowners. These arachnids adapt to indoor environments, making homes in quiet corners. Understanding them involves identifying common species, observing their behaviors, and addressing misconceptions about their potential danger.
Common House Spider Species
Several spider species commonly inhabit homes, each possessing distinct characteristics. The common house spider (Parasteatoda tepidariorum) is often encountered and typically ranges from tan to nearly black with varied patterns. Females are usually 5-6 mm long, males slightly smaller, with legs giving an inch or more spread. They construct tangled, irregular webs, often called “cobwebs,” in secluded areas like basements and crawl spaces.
The cellar spider (Pholcus phalangioides), also known as “daddy long-legs,” is another common indoor resident. They are recognizable by their extremely long, thin legs and small, pale yellow-brown, almost translucent bodies. Females typically measure about 7 to 8 millimeters, while males are around 6 millimeters. They build large, loose, flat webs, often in corners or ceilings, and may vibrate rapidly if disturbed.
Funnel weavers, like Tegenaria domestica and Eratigena atrica, are also found indoors. They are brownish or grayish, often with stripes near their head and an abdominal pattern. They construct sheet-like webs with a distinctive funnel-shaped retreat where the spider waits for prey. The yellow sac spider (Cheiracanthium mildei) has a pale green or tan body, with longer front legs. Unlike many house spiders, yellow sac spiders are nocturnal hunters that don’t build webs for prey, instead creating small, silken sacs to hide in during the day, often in wall-ceiling creases or window sills.
Behavior and Role in the Home
House spiders’ behaviors are suited to indoor habitats, focusing on shelter and food. They select undisturbed, low-light locations like upper corners, basements, attics, and crawl spaces. These areas provide the quiet, shadowy environments they prefer for constructing their webs and hunting. The common house spider randomly selects web sites; if unproductive, it abandons them to build new ones nearby, leading to numerous webs.
Many house spiders build webs, using silk to create traps for prey. The common house spider spins messy, tangled webs, while cellar spiders create loose, irregular webs. Funnel weavers build flat, horizontal webs with a funnel-shaped retreat. These webs primarily catch various household insects.
Spiders are carnivorous and play a significant role in natural pest control within the home. Their diet consists of common household insects like flies, mosquitoes, ants, moths, and cockroaches. By preying on these insects, house spiders help regulate indoor pest populations, reducing the need for chemical pesticides. Some species, like cellar spiders, also prey on other spiders.
Safety and Misconceptions
Most house spiders are generally harmless to humans. They are not aggressive and typically prefer to avoid human contact. A spider’s instinct when encountering a human is to flee and hide. Bites from common house spiders are rare, occurring only if the spider feels threatened, such as when squeezed or pressed against the skin.
The venom of most common house spiders is not medically significant to humans. While they possess venom to immobilize insect prey, its amount and potency are typically too low to cause serious harm to people. Any reaction to a bite is usually mild, resembling a minor irritation. It is a misconception that all spiders are dangerous or actively seek to bite humans while they sleep. Spiders generally perceive humans as predators and avoid contact; vibrations from a sleeping person are usually enough to deter them.