False Black Widow, Cupboard Spider, Dark Comb-Footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a globular abdomen, comb-like setae on the fourth tarsus used to pull silk over prey, and building irregular tangle webs.
Physical Description
The spider has a glossy, bulbous, egg-shaped abdomen and a relatively compact cephalothorax. The body texture appears smooth and somewhat shiny, lacking dense hairs. Sexual dimorphism is present, with females being notably larger, rounder, and possessing a more robust abdomen than the slimmer males.
Size Estimate
The body length of this specimen appears to be roughly 6 to 10 millimeters, with a leg span of approximately 20 to 25 millimeters, which is typical for an adult or sub-adult female false black widow.
Coloration & Markings
The dorsal side of the abdomen features a dark brownish-purple base color adorned with distinct, pale yellowish or cream-colored geometric markings, often forming chevron or triangular patterns. The cephalothorax and legs are a uniform dark reddish-brown, lacking any stark banding.
Web Type
Constructs a typical theridiid cobweb, which is an irregular, three-dimensional tangle of sticky silk threads spun in dark, sheltered corners, crevices, or near ground level indoors.
Eye Arrangement
Has eight small eyes arranged in two horizontal rows of four, with the lateral eyes slightly touching or closely spaced. This is characteristic of the Theridiidae family.
Leg Characteristics
Legs are moderately long and slender, tapering toward the ends, with faint darker rings visible near the joints. The fourth pair of legs possesses a serrated comb of bristles characteristic of cobweb spiders.
Venom & Safety Information
Venom Information
Possesses neurotoxic venom, but it is not nearly as potent as that of a true black widow (Latrodectus species). The venom is designed to immobilize small invertebrate prey.
Medical Significance
Minimally medically significant. A bite can cause mild localized pain, redness, and swelling similar to a wasp sting, sometimes accompanied by transient malaise. Systemic effects are rare and generally not dangerous to healthy adults.
Safety Recommendations
Avoid direct handling with bare hands. If found in living areas, gently coax the spider into a container using a piece of card and release it outdoors. Standard home hygiene and sealing cracks minimize indoor presence.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, frequently found in temperate regions worldwide. Prefers dark, humid microhabitats such as basements, crawlspaces, garage corners, under furniture, and outdoor crevices around human habitations.
Behavior & Temperament
Generally shy, timid, and non-aggressive. Nocturnal in activity, spending daylight hours hidden in its web retreat. When disturbed, it typically retreats to a corner, drops to the ground, or curls into a ball rather than attacking.
Diet & Prey
Feeds primarily on crawling and flying insects trapped in its cobweb, including flies, beetles, woodlice, cockroaches, and occasionally other spiders.
Seasonal Activity
Active year-round indoors, though sightings peak during late summer and autumn when mature males wander in search of mates. Overwinters safely within heated structures or sheltered outdoor crevices.
Description
Steatoda grossa, commonly known as the false black widow, is a frequent indoor companion in temperate homes. Often mistaken for its more dangerous relative due to its glossy, bulbous abdomen, this species is actually a beneficial household predator that helps keep insect pests in check. Its rich dark brown coloration accented by pale geometric patterns gives it a subtle, understated beauty.
Key Features
Glossy, bulbous abdomen with pale cream-colored geometric or chevron markings; dark reddish-brown legs and cephalothorax; lack of a red hourglass shape; construction of an irregular cobweb in a sheltered indoor corner.
Similar Species
True Black Widows (Latrodectus spp.), which feature a jet-black body and characteristically lack geometric dorsal markings on adults, often displaying a red hourglass underneath. Steatoda triangulosa, which has a distinct zigzag or triangular pattern on the abdomen.
Life Cycle
Females produce papery, brownish egg sacs containing up to several hundred eggs, which are guarded within the web. Spiderlings hatch after a few weeks, disperse via ballooning or crawling, and undergo multiple molts over a year to reach maturity. Lifespan can reach several years for females.
Ecological Importance
Acts as an effective natural pest controller in domestic and semi-natural environments, helping to regulate populations of nuisance insects like flies, roaches, and woodlice.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and thriving globally, often expanding their range alongside human habitation.
Interesting Facts
Despite the alarming 'false widow' moniker, these spiders are extremely docile and will only bite if firmly pressed against human skin. They are known to occasionally prey on true black widows that wander into their webs.
Photography Tips
Use macro lenses with adequate lighting or a ring flash to capture the subtle pale geometric patterns on the dark abdomen. Photograph from a side or top-down angle while the spider is stationary in its web.
Identified: 2026-10-19T16:54:34.651921