False Widow Spider, Cupboard Spider, Dark Cobweb Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a globular abdomen, comb-like serrated bristles on the tarsus of the fourth leg used to pull silk from the spinnerets, and untidy, three-dimensional tangle webs.
Physical Description
The spider has a bulbous, glossy, button-like abdomen and a distinctively smaller, oval cephalothorax. The overall texture is smooth to slightly glossy with fine hairs. Females are notably larger and more rounded than males.
Size Estimate
Body length ranges from 6 to 10.5 mm for females and 4 to 6 mm for males, with a leg span up to 25 mm. The specimen shown appears to be a smaller adult or subadult.
Coloration & Markings
Deep purplish-brown to black or dark reddish-brown, often featuring pale yellowish or cream-colored markings, typically in the form of crescent shapes or triangular spots on the dorsal abdomen. Some specimens exhibit a faint button-like pattern.
Web Type
Builds a sticky, irregular, three-dimensional cobweb (tangle web) in dark, sheltered crevices, typically close to the ground, under furniture, or in corners.
Eye Arrangement
Eight small eyes arranged in two horizontal rows of four, typical of the Theridiidae family, with lateral eyes often touching or closely grouped.
Leg Characteristics
Long, slender, tapering legs with minimal spination, often matching the dark brown body coloration with faint darker banding.
Venom & Safety Information
Venom Information
Neurotoxic venom typical of theridiids, though significantly less potent than that of true widows (Latrodectus). Causes mild to moderate localized pain, swelling, and redness.
Medical Significance
Low medical significance. While bites can be painful and occasionally produce localized swelling, malaise, or mild fever, they are generally not dangerous and do not cause necrotic wounds.
Safety Recommendations
Avoid direct handling with bare hands. If found under furniture or in living spaces, gently coax the spider into a container using a piece of card and release it outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; highly synanthropic in temperate regions like the UK (including Liverpool), frequently found indoors in dark undisturbed areas, garages, sheds, and beneath furniture, as well as outdoors under rocks and bark.
Behavior & Temperament
Timid and non-aggressive; hangs upside down in its web and retreats rapidly when disturbed, only biting if trapped tightly against human skin.
Diet & Prey
Generalist predator feeding on crawling insects, woodlice, flies, and other spiders caught in its sticky web.
Seasonal Activity
Active year-round indoors due to climate-controlled environments, with peak wandering and mating activity observed during late summer and autumn.
Description
Steatoda grossa, widely known as the false widow or cupboard spider, is a frequent indoor companion in temperate regions. With its glossy, bulbous abdomen and dark coloration, it is often mistaken for the true black widow, but it lacks the iconic red hourglass marking. It spends its life quietly waiting in a tangled web underneath furniture or in dark corners, helping naturally control household insect pests.
Key Features
Glossy, bulbous dark abdomen, lack of red hourglass markings, presence of pale cream or yellowish crescent markings on the dorsal side, and association with messy corner cobwebs.
Similar Species
Steatoda nobilis (Noble False Widow, which has more distinct angular markings), Steatoda bipunctata (Rabbit Hutch Spider, smaller with distinct white spots), and Latrodectus species (True Widows, which feature bright red ventral or dorsal markings).
Life Cycle
Females produce several whitish-brown silk egg sacs containing up to 200 eggs each. Spiderlings disperse via ballooning or crawling. They can live for several years in protected indoor environments.
Ecological Importance
Serves as an effective natural pest controller in domestic and garden environments, helping regulate populations of flies, beetles, and other arthropods.
Conservation Status
Not evaluated by the IUCN, but highly secure and expanding its range globally due to human commerce and indoor habitat adaptation.
Interesting Facts
False widows are known to prey upon other household spiders, including larger species and even funnel-web spiders, by using their strong silk and comb-feet to subdue prey.
Photography Tips
Use macro lenses with good lighting (diffused flash) to highlight the glossy texture and pale patterns on the dorsal abdomen without disturbing the timid spider.
User Notes
Under chair in Liverpool
Identified: 2026-08-14T10:16:53.864494