Common House Spider (Parasteatoda tepidariorum) - Identification, Range & Medical Data

Summary

The most frequently encountered indoor spider across temperate North America. Often confused with widow spiders because of its similar tangled cobweb and spherical abdomen, but its mottled brown coloration and small size distinguish it.

Quick answers

Is Common House Spider dangerous to humans?: No. Current evidence does not link common house spider bites to serious medical outcomes in healthy adults.
How big is an adult common house spider?: Adult female body length is 5–8 mm; males are 3–5 mm. Leg span reaches 20–30 mm.
Where does Common House Spider live?: Indoors: ceiling corners, behind furniture, garages, basements, sheds. Rarely outside structures in cooler climates. Established U.S. populations occur in 1 states.
What does Common House Spider eat and when is it active?: Flies, mosquitoes, small moths, ants, other small spiders. Sedentary on the web; active year-round indoors.

Identification

Body 5–8 mm with mottled tan and brown abdomen, often with cream chevrons
Spherical abdomen, comparatively long legs
Builds messy, persistent cobwebs in upper corners
Female often visible suspended belly-up in the web

Morphometrics

Measurement	Female	Male
Body length	5–8 mm	3–5 mm
Leg span	20–30 mm	-
Lifespan	1–2 years	-

Trait	Value
Web type	Tangled three-dimensional cobweb, often persistent in upper corners.
Eye arrangement	Eight eyes in two rows of four.
Eggs per sac	150–400
Egg sacs per year	3–17

Geographic range

Native range: Cosmopolitan synanthrope - found worldwide in human-built structures; native range uncertain (likely South America).

U.S. states with established populations: All 50 U.S. states.

State pages covering Common House Spider

Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming

Habitat & behavior

Habitat: Indoors: ceiling corners, behind furniture, garages, basements, sheds. Rarely outside structures in cooler climates.

Activity: Sedentary on the web; active year-round indoors.

Diet: Flies, mosquitoes, small moths, ants, other small spiders.

Venom & medical significance

Venom property	Value
Type	Not medically significant
LD₅₀	Not established
Note	-

Bite symptoms & first aid

Symptoms

Bites are extremely rare and produce only minor local irritation

Commonly confused with

Black widow (juvenile)
Brown widow
False widow

Key facts

The common house spider is one of the most studied model organisms in arachnology, with a sequenced genome used to study segmentation and silk biology. [1]

Sources

[1]Common House Spider - Penn State Extension. Accessed 2026-06-14.