Cupboard Spider, False Black Widow, Dark Cobweb Spider
Steatoda grossa
Theridiidae (Tangle-web spiders), Order Araneae. Key family characteristics include a rounded, bulbous abdomen, comb-like serrated bristles on the tarsus of the fourth pair of legs used for flinging silk over prey, and irregular, three-dimensional cobwebs.
Physical Description
The spider features a shiny, bulbous, egg-shaped abdomen and a distinctively narrower cephalothorax. The body texture is smooth and glossy, with minimal hair. Females are noticeably larger and rounder than males, which have slightly slender abdomens and longer relative leg spans.
Size Estimate
Body length ranges from 6 to 10.5 mm for females and 4 to 6 mm for males. The total leg span can reach up to 25 to 30 mm, consistent with a typical adult specimen.
Coloration & Markings
Deep purplish-brown to glossy black base coloration, sometimes appearing dark reddish-brown. It often features subtle, pale yellowish or grayish markings, including a crescent-shaped band across the anterior portion of the dorsal abdomen and faint diagonal chevrons.
Web Type
Builds an irregular, sticky, three-dimensional tangle web commonly known as a cobweb. It is typically constructed in dark, sheltered locations such as corners, crevices, under furniture, inside cupboards, or around structural foundations.
Eye Arrangement
Consists of eight small eyes arranged in two horizontal rows of four, typical of the family Theridiidae. The eyes are relatively uniform in size, set closely together on a slightly raised tubercle.
Leg Characteristics
Long, slender legs with subtle darker banding toward the joints. The legs lack prominent spines but are equipped with specialized comb-like structures on the hind tarsi for manipulating sticky silk during prey capture. They rest with legs splayed outward in the web.
Venom & Safety Information
Venom Information
Possesses neurotoxic venom designed for subduing arthropod prey. While often referred to as a false black widow, its venom is significantly less potent than that of true widows (Latrodectus species).
Medical Significance
Not considered medically significant. A bite is rare and typically only occurs when the spider is trapped directly against human skin. Symptoms are generally mild, including localized pain, redness, and minor swelling, occasionally accompanied by mild systemic effects like malaise or a mild headache in sensitive individuals.
Safety Recommendations
Avoid handling spiders with bare hands. If found inside a living space, gently relocate the spider outdoors using a glass and a piece of card. Standard household cleaning and sealing entry points help reduce indoor populations.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, found worldwide in temperate regions, including North America, Europe, Australia, and New Zealand. Strongly synanthropic, favoring human dwellings, outbuildings, garages, woodpiles, and dark crevices.
Behavior & Temperament
Docile and non-aggressive. They are strictly nocturnal web-dwellers that spend most of their time hanging motionless upside down in their webs. When disturbed, they typically retreat rapidly, drop to the ground, or curl into a defensive ball rather than bite.
Diet & Prey
Feeds primarily on crawling and flying insects trapped in its web, including ants, woodlice, flies, beetles, and occasionally other spiders. It uses its sticky silk and comb feet to rapidly wrap prey before delivering a paralyzing bite.
Seasonal Activity
Active year-round indoors, though sightings peak during late summer and autumn when mature males wander in search of females during the mating season. They overwinter in sheltered crevices as adults or older juveniles.
Description
The False Black Widow (Steatoda grossa) is a common yet often misunderstood household spider. With its glossy, rounded dark body and preference for quiet corners, it frequently startles homeowners who mistake it for its infamous relative, the black widow. In reality, this quiet cobweb weaver is a beneficial household resident that helps control nuisance insect populations without seeking out human contact.
Key Features
Glossy, bulbous dark brown to black abdomen, absence of a red hourglass marking, presence of faint pale yellowish or cream-colored crescent markings near the front of the abdomen, and an irregular tangle web built close to the ground or in dark corners.
Similar Species
True Black Widow (Latrodectus species): Distinguished by the classic red hourglass marking on the ventral abdomen and a jet-black, satin-finish body. Steatoda triangulosa (Triangle Weaver): Features a distinct triangular patterned marking on the abdomen rather than solid dark tones.
Life Cycle
Females produce several whitish or brownish silk egg sacs containing up to 200 eggs each, typically hidden within the web structure. Spiderlings hatch after a few weeks, disperse via ballooning or crawling, and undergo multiple molts over a year to reach maturity. Lifespan can exceed several years for females.
Ecological Importance
Acts as an effective natural pest controller in and around human habitations, consuming large quantities of crawling insects, flies, and structural pests. Serves as a food source for larger predators such as birds, small mammals, and predatory wasps.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and thriving globally due to their close association with human habitations.
Interesting Facts
Despite their common name 'false black widow', Steatoda species can sometimes prey on true black widows by entering their webs, using superior silk-wrapping techniques to subdue them. They are also remarkably long-lived for araneomorph spiders, with females sometimes surviving for up to six years.
Photography Tips
Use macro photography with diffuse natural lighting or a ring flash to capture the glossy texture of the abdomen without harsh glare. Shoot from a side angle to highlight the rounded body proportions and subtle pale markings.
Identified: 2026-08-29T21:06:16.676763