Common American House Spider
Parasteatoda tepidariorum
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider has a bulbous, globular abdomen that is noticeably larger than its cephalothorax. It has a high-domed silhouette and slender legs, typical of comb-footed spiders.
Size Estimate
Body length ranges from 5 to 8 mm for females and slightly smaller for males, with a leg span of approximately 15 to 25 mm.
Coloration & Markings
Mottled brown and grayish-tan coloration with darker chevron markings or spots along the upper surface of the abdomen, providing camouflage against structural surfaces.
Web Type
Tangle web or cobweb, consisting of a messy, irregular three-dimensional network of silk threads constructed in corners, crevices, and under eaves.
Eye Arrangement
Eight small eyes arranged in two rows of four, set closely together on a slightly raised tubercle on the front of the cephalothorax.
Leg Characteristics
Long, slender legs with distinct dark and light banding. The hind legs feature a comb of serrated bristles used for pulling silk from the spinnerets.
Venom & Safety Information
Venom Information
Neurotoxic venom primarily targeted at invertebrate prey. It is low in potency regarding humans and rarely causes systemic issues.
Medical Significance
Not medically significant. Bites are extremely rare, usually occurring only when trapped against the skin, and typically result in mild, localized pain and minor swelling.
Safety Recommendations
Leave them alone as beneficial pest controllers. If relocation is necessary, gently guide the spider into a container using a piece of paper.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, frequently found in association with human habitations, including basements, crawlspaces, porches, and outbuildings.
Behavior & Temperament
Non-aggressive and very timid. They hang upside down in their webs and retreat rapidly when disturbed.
Diet & Prey
Feeds on a wide variety of household and garden insects, including flies, mosquitoes, beetles, and other spiders, capturing them via sticky web threads.
Seasonal Activity
Active year-round indoors, with peak mating and egg-laying activity occurring during the warmer spring and summer months.
Description
The Common American House Spider is a familiar nocturnal architect of quiet corners and dusty rafters. With its globular abdomen and haphazard web, it acts as an efficient and harmless pest controller around human dwellings.
Key Features
Globular abdomen, mottled brown coloration, irregular cobweb structure, and the presence of a comb-like row of setae on the fourth tarsus.
Similar Species
Steatoda grossa (False Black Widow), which is darker, glossier, and more robustly built with purplish-brown tones.
Life Cycle
Females produce brownish, pear-shaped papery egg sacs containing hundreds of eggs, hanging them within the web structure. Spiderlings disperse via ballooning after hatching.
Ecological Importance
Serves as a natural pest control agent by intercepting and consuming flying and crawling insects around homes and gardens.
Conservation Status
Not evaluated by the IUCN, but highly secure and abundant globally due to its close association with human environments.
Interesting Facts
These spiders can adjust the tension of their web threads to optimize the detection of struggling prey of various sizes.
Photography Tips
Use a macro lens with a flash or diffused side-lighting to highlight the intricate patterns on the rounded abdomen while maintaining a safe focal distance.
Identified: 2026-09-17T22:35:37.493291