Facts, Identification & Control
House spiders occur throughout the world and have derived their name from their presence inside human dwellings. A number of species are classified as house spiders, although the common house spider is the most recognized. These arachnids are also sometimes referred to as American house spiders.
Female common house spiders measure 5 to 8 mm in length, while males measure only 4 mm. Common house spiders are typically brown or gray in color, with darker chevron markings along their bodies.
A house spider’s body is divided into the cephalothorax and the abdomen. Like scorpions, mites and ticks, house spiders are wingless. They are classified as arachnids rather than insects and have eight, single-lens eyes.
Behavior, Diet & Habits
House spider webs are irregularly shaped and can be located in various places within a home, including windows, ceiling corners and above or beneath fixtures.
The presence of common house spiders is typically characterized by the formation of cobwebs. These silken thread structures can be found throughout infested homes. This abundance of empty webs is caused by the common house spider’s propensity to spin webs in various locations until it finds the most suitable place to catch prey.
Webs are designed as trapping mechanisms and are funnel-shaped, with the narrow end acting as a den for the arachnid. Any contact made with the web produces vibrations throughout the strand, signaling to the common house spider that prey is present. Although common house spiders feed primarily on insects, they may also consume larger spiders, scorpions, rodents and small reptiles.
Life Cycle & Reproduction
Female common house spiders (Parasteatoda tepidariorum) deposit as many as 250 eggs into a sac of silk. These sacs are often brown in color and are flask-like in shape. Females produce up to 17 of these sacs during a lifetime, resulting in more than 4,000 eggs.
Within a week, spiderlings hatch and begin to undergo a series of instars. The first instar takes place inside the egg sac. Males undergo six instars, while females undergo seven. After hatching, air currents disperse surviving spiderlings on threads of silk. This process, known as ballooning, allows spiders to populate habitats far from their origin.
Adult specimens may survive for more than a year. Their exteriors and sternums are yellow or brown in color. Their abdomens are gray and marked with white, while their legs are brown and darkly banded. Males are smaller than females, measuring only 4 mm in length as opposed to the female’s 8 mm.
Unlike some other spider species, male and female common house spiders may choose to cohabitate and mate numerous times.
Signs of a House Spider
Signs of house spider infestations include the spider and their webs.
Do House Spiders Bite?
House spiders rarely bite unless they feel threatened. However, spiders may defend themselves when crushed in shoes or clothing being put on by a human.
The bites of house spiders are not medically threatening. In the event of severe swelling, lesions or headaches, victims should immediately seek medical attention. If possible, take the spider along for proper identification. It is best to allow a medical professional to determine the best treatment.
Prevention methods begin with exclusion. Windows and doors should be tightly fitted and any cracks or gaps around the exterior should be sealed. Webs should be removed when seen to eliminate the eyesore and to discourage the spiders from building.
The first step in controlling house spider populations is locating possible entry points. They often enter through gaps around windows and doors. Sealing these openings is critical to reduce possible future house spider invasions. Window and door screens can prevent the entry of other insect pests, and the use of door sweeps is suggested. Cracks and other voids within walls and foundations should be sealed with caulking. Following exclusion, homeowners may choose to vacuum to remove webs and egg sacs. Outside, webs can be knocked down.
Types of House Spiders
Brown House Spiders (Steatoda grossa)
Red House Spiders (Nesticodes rufipes)
Black House Spiders (Badumna insignis)
Giant House Spiders (Eratigena atrica)
Southern House Spiders (Kukulcania hibernalis)
Domestic House Spiders (Tegenaria domestica)