Common House Spider, American House Spider
Parosteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A small-to-medium spider featuring a large, bulbous, almost teardrop-shaped abdomen that is significantly taller than it is wide. The cephalothorax is small and relatively flat. Females are much larger than males and have a more pronounced abdominal swell.
Size Estimate
Body length typically 5–8 mm (0.2–0.3 in) for females; leg span approximately 20–30 mm. This specimen appears to be an adult female.
Coloration & Markings
Variable mottled patterns of tan, brown, and grey with white patches. A dark 'V' or chevron-shaped pattern is often visible on the back of the abdomen. Legs are typically tan with dark bands at the joints.
Web Type
Messy, tangled 'cobwebs' built in corners, under furniture, or near windows. Often features a more densely woven retreat area where the spider hides.
Eye Arrangement
Eight eyes arranged in two rows of four; typical of Theridiidae where the eyes are relatively small and the lateral eyes are often touching.
Leg Characteristics
Long, slender legs with the first pair being the longest. They feature serrated bristles on the tarsus (the 'comb-foot') used to fling silk over prey.
Venom & Safety Information
Venom Information
Contains neurotoxins used to paralyze insect prey. However, the venom is not considered medically significant to humans.
Medical Significance
Low danger level. Bites are rare and usually only occur if the spider is squeezed. Symptoms typically include local redness, minor swelling, and itching similar to a bee sting.
Safety Recommendations
Harmless and best left alone to provide free pest control. If relocation is desired, use the cup-and-paper method to move them outdoors to a shed or porch.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found throughout the world. Primarily found in and around human structures, barns, and sheds.
Behavior & Temperament
Very timid and non-aggressive. When threatened, they usually retreat to a corner or drop to the floor on a dragline. They are passive hunters that wait for prey to stumble into their silk traps.
Diet & Prey
Insects such as flies, mosquitoes, ants, and larger arthropods; they are known to occasionally capture and feed on other spiders and small centipedes.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though sightings increase in late summer and autumn as populations peak.
Description
The quintessential 'cobweb spider,' this species is a master of domestic life. Its mottled brown appearance allows it to blend into dust and shadows, while its tangled web is an effective snare for indoor pests. It is a quiet, beneficial roommate seen in almost every household.
Key Features
High, bulbous abdomen; mottled tan/brown coloration; banded legs; comb-feet; messy tangled web; pear-shaped brown egg sacs.
Similar Species
Steatoda grossa (False Black Widow) which is darker and lacks the mottling; Latrodectus (Black Widow) which is shiny black with a red hourglass.
Life Cycle
Females produce brown, pear-shaped, papery egg sacs. A single female can produce several sacs a year, each containing hundreds of eggs. Spiderlings disperse via 'ballooning'.
Ecological Importance
Highly beneficial for natural pest control; they consume vast quantities of household pests including flies, roaches, and mosquitoes.
Conservation Status
Not evaluated by IUCN; however, they are extremely common and widespread with no known threats to their population.
Interesting Facts
Despite their small size, they can tackle prey much larger than themselves by using their 'comb-feet' to wrap insects in silk from a distance before delivering a bite.
Photography Tips
Focus on the abdomen pattern and the bands on the legs. Using a macro lens or digital zoom is helpful due to their small size and the distracting nature of their silk webs.
Identified: 2026-06-15T04:59:27.845546