Cupboard Spider, False Black Widow, Dark Cobweb Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include the presence of a comb-like row of serrated bristles on the tarsus of the fourth pair of legs, used to pull silk from the spinnerets.
Physical Description
Features a bulbous, glossy, globular abdomen that overhangs the small cephalothorax. The body texture appears smooth and shiny with a leathery finish. Strong sexual dimorphism is present, with females being significantly larger and more globose than males.
Size Estimate
Body length ranges from 6 to 10.5 mm for adult females, and 4 to 6 mm for males. Leg span is typically around 20 to 25 mm. This specimen appears to be an adult female.
Coloration & Markings
Deep brownish-purple to nearly black base coloration with subtle pale yellowish or cream markings, often forming chevron or crescent patterns on the dorsal abdomen, though some individuals may appear uniformly dark.
Web Type
Builds an irregular, sticky tangle web often referred to as a cobweb, typically constructed in dark, sheltered crevices near ground level or in undisturbed corners of human dwellings.
Eye Arrangement
Eight small eyes arranged in two horizontal rows of four, typical of the Theridiidae family, set on small tubercles on the anterior cephalothorax.
Leg Characteristics
Long, slender, tapering legs with minimal spination compared to hunting spiders. They are typically reddish-brown to dark brown, matching the body, and lack prominent banding.
Venom & Safety Information
Venom Information
Possesses neurotoxic venom (latrotoxin-like), but it is significantly less potent than that of Latrodectus (widow) species. Not considered medically dangerous to humans.
Medical Significance
Minor medical significance. A bite can cause localized pain, redness, and swelling lasting a few hours, occasionally accompanied by mild systemic symptoms like malaise or headache, but severe envenomation is rare.
Safety Recommendations
Wear gloves when cleaning undisturbed areas like basements or woodpiles. Relocate spiders gently using a cup and paper if found inside living spaces.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution found worldwide in temperate regions. Commonly inhabits human-made structures, basements, garages, hollow trees, and under loose bark or rocks outdoors.
Behavior & Temperament
Docile and non-aggressive. They spend most of their time hanging upside down in their webs. When disturbed, they typically retreat, drop from the web, or curl up defensively rather than bite.
Diet & Prey
Feeds primarily on crawling insects, woodlice, and other spiders, including occasionally dangerous species like true widow spiders, using sticky silk threads to subdue prey.
Seasonal Activity
Active year-round indoors, with peak mating and wandering activity occurring during the late summer and autumn months.
Description
The cupboard spider is a frequent indoor companion that often goes unnoticed in dark corners. With its glossy, rounded abdomen and web-bound lifestyle, it serves as a master of quiet pest control in and around homes.
Key Features
Glossy, bulbous, teardrop-to-round abdomen, dark reddish-purple to black coloration, lack of a red hourglass marking, and messy cobweb construction.
Similar Species
Latrodectus species (Black Widows). Distinguished by the absence of the bright red hourglass marking on the ventral side and a generally browner, less velvety black appearance.
Life Cycle
Females produce brownish silken egg sacs containing up to several hundred eggs. Spiderlings disperse via ballooning after hatching. They undergo multiple molts over a lifespan of 1 to 3 years.
Ecological Importance
Acts as an effective natural pest controller in domestic and wild ecosystems, suppressing populations of crawling insects and other arthropods.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and thriving globally alongside human settlements.
Interesting Facts
Despite being called the False Black Widow, they occasionally prey on actual black widows by invading their webs and wrapping them up using superior silk-casting techniques.
Photography Tips
Use macro lenses with adequate side-lighting to highlight the glossy texture of the abdomen without causing distracting harsh reflections. Keep a safe, steady distance.
Identified: 2026-07-30T03:03:54.626590