False Black Widow, Cobweb Spider, Cupboard Spider
Steatoda grossa
Family Theridiidae (Cobweb Spiders), Order Araneae. Characterized by a globular abdomen, comb-like serrated bristles on the tarsus of the fourth leg, and building irregular tangle webs.
Physical Description
Robust body shape with a glossy, bulbous, egg-shaped abdomen and a relatively small cephalothorax. Smooth, shiny integument without dense hair, giving a sleek appearance.
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 about 20 to 30 mm. This specimen appears to be an adult female.
Coloration & Markings
Deep purplish-brown to dark brownish-black base coloration with subtle pale yellowish or cream-colored geometric markings, often forming crescents or chevron patterns on the dorsal abdomen.
Web Type
Irregular tangle web, commonly known as a cobweb. Constructed in dark, undisturbed corners, crevices, or near ground level indoors, featuring sticky vertical lines designed to entangle walking prey.
Eye Arrangement
Eight small eyes arranged in two parallel, slightly curved rows of four across the front of the cephalothorax, typical of the Theridiidae family.
Leg Characteristics
Long, slender legs with distinct dark banding or shading. The legs lack heavy spines but are equipped with specialized serrated bristles on the hind tarsi for manipulating silk.
Venom & Safety Information
Venom Information
Neurotoxic venom typical of cobweb spiders, but significantly less potent than that of true widow spiders (Latrodectus).
Medical Significance
Low medical significance. Bites are rare and usually occur only when pressed against human skin. Symptoms are typically mild and localized, including minor swelling, redness, and pain lasting a few hours, occasionally accompanied by mild systemic effects like malaise.
Safety Recommendations
Practice caution when reaching into dark, undisturbed storage spaces. Relocate spiders gently using a cup and card if found in living areas rather than using chemicals.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, highly synanthropic. Frequently found worldwide in temperate and subtropical regions, inhabiting dark corners of human dwellings, garages, sheds, under furniture, and outdoor rock crevices.
Behavior & Temperament
Timid and non-aggressive. Nocturnal hunter, spending most of its time hanging upside down in its web. Will retreat when disturbed or curl into a ball and 'play dead'.
Diet & Prey
Generalist predator feeding on crawling and flying insects such as flies, beetles, woodlice, cockroaches, and occasionally other spiders.
Seasonal Activity
Active year-round indoors, with increased visibility and wandering behavior during late summer and autumn when males search for mates.
Description
The False Black Widow is a frequent indoor companion that often goes unnoticed until spotted in a dim corner. Recognized by its glossy, bulbous abdomen and rich dark brown to purplish tones, it shares a superficial silhouette with its notorious black widow relatives but lacks the stark red hourglass marking. As an expert pest controller in and around human structures, it quietly manages indoor insect populations.
Key Features
Glossy, bulbous dark brown abdomen with pale cream-colored markings, lack of a red hourglass shape, and a preference for building messy tangle webs in corners.
Similar Species
Latrodectus species (True Widow Spiders), which possess bright red or orange hourglass markings underneath the abdomen and jet black coloration.
Life Cycle
Females construct brownish silk egg sacs containing up to several hundred eggs. Spiderlings hatch after a few weeks, disperse via ballooning or crawling, and molt multiple times over a lifespan of several years for females.
Ecological Importance
Serves as an effective natural pest control agent in domestic and agricultural settings by reducing populations of nuisance insects.
Conservation Status
Not evaluated by the IUCN, but secure and widely distributed globally due to strong association with human habitats.
Interesting Facts
Despite the intimidating common name, Steatoda grossa is remarkably docile and has been known to successfully prey on much larger spiders and insects, including venomous species.
Photography Tips
Use macro lenses with a ring flash or diffused external lighting to capture the subtle pale patterns on the glossy abdomen without creating harsh reflections.
Identified: 2026-08-25T07:47:53.857837