Cupboard Spider, False Black Widow, Dark Cobweb Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The body is robust and bulbous with a shiny, smooth texture. The cephalothorax is relatively compact and dark, while the abdomen is large, globose, and domed, overhanging the cephalothorax slightly.
Size Estimate
Body length typically ranges from 6 to 10.5 mm for females and 4 to 7 mm for males, with a leg span up to 25 mm.
Coloration & Markings
Deep purplish-brown to black coloration, often featuring pale yellowish or grayish markings on the dorsal abdomen, including subtle chevron patterns or spots.
Web Type
Tangle web or irregular cobweb constructed in dark, sheltered crevices using sticky, viscid silk.
Eye Arrangement
Eight small eyes arranged in two rows of four, typical of the family Theridiidae, with lateral eyes positioned closely together in pairs.
Leg Characteristics
Long, slender legs with distinct dark and light banding patterns, bearing fine setae and lacking heavy spination.
Venom & Safety Information
Venom Information
Contains neurotoxic components (latrotoxin-like), though significantly milder than true widow spiders. Envenomation causes localized pain and minor systemic symptoms.
Medical Significance
Not medically significant. Bites are uncommon and typically result in mild, localized pain, redness, and occasionally blistering that resolves without intervention.
Safety Recommendations
Avoid handling with bare hands; if found indoors, gently relocate using a cup and a piece of paper. No special pest control is generally necessary.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found globally in temperate and subtropical regions, typically inhabiting dark corners of buildings, basements, under furniture, and outdoor crevices.
Behavior & Temperament
Reclusive, nocturnal, and non-aggressive. They hang upside down in their webs and retreat when disturbed, rarely biting unless directly trapped or squeezed.
Diet & Prey
Feeds primarily on crawling insects, woodlice, and other spiders, occasionally subduing larger prey using strong sticky silk threads.
Seasonal Activity
Active year-round indoors, with peak mating and wandering activity during the warmer summer and autumn months.
Description
Steatoda grossa, widely known as the false black widow, is a frequent indoor companion found inhabiting quiet corners and structural crevices. Its glossy, bulbous abdomen and dark, banded legs give it a distinct appearance that often causes confusion with more dangerous relatives.
Key Features
Glossy, globose abdomen, lack of a red hourglass marking, dark banded legs, and preference for irregular cobwebs in dark indoor spaces.
Similar Species
Latrodectus species (Black Widows), which feature the diagnostic red hourglass marking and lack distinct leg banding.
Life Cycle
Females produce brownish silken egg sacs containing up to several hundred eggs, guarding them in the web until spiderlings hatch and disperse.
Ecological Importance
Acts as an effective natural pest controller in domestic and peri-domestic environments by reducing populations of crawling insects.
Conservation Status
Not evaluated by the IUCN, but populations are stable, widespread, and thriving globally due to human habitation.
Interesting Facts
Despite the frightening common name, false widows play a beneficial role in controlling household pests and can live for several years in captivity.
Photography Tips
Use macro lenses with adequate lighting to capture the glossy texture of the abdomen and the subtle banding patterns on the legs while maintaining a safe distance.
Identified: 2026-08-30T18:59:08.692262