False Black Widow, Cupboard Spider, Dark Comb-Footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A medium-sized spider with a shiny, bulbous, globe-shaped abdomen and a smaller cephalothorax. The surface is smooth and lacks the dense hair found on wolf spiders. Females have a significantly more robust abdomen than males.
Size Estimate
Body length 6-11mm for females; leg span approximately 15-25mm. This specimen appears to be an adult female based on the abdominal volume.
Coloration & Markings
Dark purple-brown to blackish base color. Typically features a light-colored, crescent-shaped band on the anterior portion of the abdomen, sometimes accompanied by pale spots or chevrons along the dorsal midline.
Web Type
Tangle web or 'cobweb'. A messy, irregular three-dimensional scaffold of sticky silk, usually built in dark corners, under furniture, or in crevices.
Eye Arrangement
8 eyes in two rows; typical of Theridiidae where eyes are relatively small and the lateral eyes are positioned close together.
Leg Characteristics
Slender, dark brown or reddish-brown legs. Possesses a 'comb' of serrated bristles on the tarsi of the fourth pair of legs, used to wrap prey in silk.
Venom & Safety Information
Venom Information
Contains alpha-latrotoxin-like components but much less potent than true widows. Can cause localized pain, blistering, and occasionally mild systemic malaise.
Medical Significance
Low. Not considered dangerous to healthy humans. Bites are rare and usually occur only if the spider is squeezed against skin. Pain is comparable to a bee sting.
Safety Recommendations
If relocation is desired, use the 'cup and card' method. Wear gloves when cleaning dark, undisturbed areas like garages to avoid accidental 'pinch' bites.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Highly synanthropic, preferring man-made structures such as basements, garages, sheds, and crawl spaces.
Behavior & Temperament
Sedentary, nocturnal ambush hunter that stays within its web. Extremely shy and non-aggressive; typically retreats or plays dead (thanatosis) when disturbed.
Diet & Prey
Generalist predator of crawling insects, pill bugs, and other spiders. Known to occasionally prey on true Black Widows (Latrodectus).
Seasonal Activity
Active year-round in indoor or sheltered environments; peak mating and activity often observed in late summer and autumn.
Description
The Steatoda grossa is a common household resident often mistaken for its more dangerous cousins. With its sleek, dark, rounded abdomen, it acts as a silent guardian of the home, consuming invasive pests and even other spiders from its inconspicuous corner web.
Key Features
Glossy bulbous abdomen, lack of a red hourglass marking, white/pale crescent on the front of the abdomen, and 'comb-footed' leg structure.
Similar Species
Latrodectus mactans (Black Widow) - distinguished by the red hourglass; Steatoda nobilis (Noble False Widow) - distinguished by a 'pentagon' or skull-like pattern on the abdomen.
Life Cycle
Females produce round, papery, white/cream egg sacs containing 40-100 eggs. They can live up to 6 years, while males typically live much shorter lives and die shortly after mating.
Ecological Importance
Critical predator in urban micro-ecosystems, providing significant pest control by consuming woodlice, cockroaches, and flies.
Conservation Status
Not evaluated (Common). Population is stable and expanding due to human transit and urbanization.
Interesting Facts
Despite their similar appearance, False Widows are often used as biological control agents in homes to naturally reduce populations of more venomous spiders.
Photography Tips
Focus on the dorsal (top) pattern of the abdomen and the shape of the cephalothorax. Using a flashlight can help highlight the subtle purple/brown tones against the dark body.
Identified: 2026-05-21T19:38:20.687594