False Black Widow, Cupboard Spider, Dark Comb-Footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
Small-to-medium cobweb spider featuring a bulbous, oval-to-globular abdomen and a smaller, oval cephalothorax. The body surface is smooth and slightly glossy. Females possess a significantly larger, rounded abdomen, while males are slimmer with longer legs relative to their body size.
Size Estimate
Estimated body length of 6-9 mm with a leg span of approximately 15-20 mm, typical for an adult female or subadult Steatoda grossa.
Coloration & Markings
Deep reddish-brown to dark chocolate brown cephalothorax and legs, with a lighter tan or purplish-brown bulbous abdomen displaying faint crescent-shaped or pale chevron markings along the dorsal midline.
Web Type
Irregular, three-dimensional tangle web or cobweb constructed in quiet, dark corners, wall bases, trim, or behind furniture.
Eye Arrangement
Eight eyes arranged in two transverse rows of four across the front of the carapace, typical of the family Theridiidae.
Leg Characteristics
Slender, moderately long legs with a light yellowish-brown to reddish-brown coloration, featuring comb-like bristles (serrated setae) on the tarsus of the fourth pair of legs used for slinging silk.
Venom & Safety Information
Venom Information
Contains mild neurotoxic venom used to immobilize prey. Bites to humans are extremely rare and generally minor compared to true black widows (Latrodectus species).
Medical Significance
Not medically dangerous. Bites may cause localized pain, minor swelling, redness, and occasionally mild headache or nausea lasting a few hours to a day; symptoms resolve without severe complications.
Safety Recommendations
Harmless to humans; if relocation is desired, gently trap the spider using a clear glass container and card, then release it outdoors near a garden shed or leaf litter.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution widely found across North America, Europe, Australia, and parts of Asia. Highly synanthropic, preferring dark, sheltered indoor environments like basements, wall trim, garages, cupboards, and crawl spaces.
Behavior & Temperament
Timid, nocturnal, and highly non-aggressive spider that spends most of its time motionless in its web, fleeing or dropping to the floor when disturbed.
Diet & Prey
Generalist predator feeding on crawling insects such as ants, beetles, woodlice, flies, and occasionally other spiders.
Seasonal Activity
Active year-round indoors in climate-controlled environments; peak mating and egg-laying occur during warm spring and summer months.
Description
Steatoda grossa, commonly known as the False Black Widow, is a common synanthropic spider often mistaken for true black widows due to its dark, glossy appearance and bulbous abdomen. Unobtrusive and beneficial, it controls common household pests from the safety of its tangled silk web.
Key Features
Glossy reddish-brown to dark brown body, bulbous abdomen with faint pale crescent or chevron patterns, lack of a red hourglass marking on the underside, and tarsal comb on the hind legs.
Similar Species
Latrodectus mactans (Southern Black Widow, distinguished by a bright red hourglass on the ventral abdomen), Steatoda nobilis (Noble False Widow, features a distinct ivory skull-like marking), and Parasteatoda tepidariorum (Common House Spider, lighter tan with variegated patterns).
Life Cycle
Females produce round, whitish to pale tan silk egg sacs hidden near their web containing dozens of eggs. Spiderlings disperse after hatching, and adults can live for 1 to 6 years.
Ecological Importance
Serves as an efficient indoor predator controlling populations of household insect pests and small arthropods.
Conservation Status
Not evaluated (Least Concern); secure population with stable trends due to human cohabitation.
Interesting Facts
Despite their sinister nickname, false widows are effective natural pest controllers in homes and have even been known to prey upon true black widows where their ranges overlap.
Photography Tips
Use a macro lens with diffuse flash to highlight the abdominal patterns and contrast the dark brown body against light trim or wall surfaces.
Identified: 2026-07-23T23:17:59.250400