False Black Widow, Cupboard Spider, Bitten Spider, Dark Comb-Footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key features include a globose abdomen and a 'comb' of serrated bristles on the fourth tarsi.
Physical Description
A medium-sized spider with a very large, bulbous, or 'globose' abdomen that is much larger than the cephalothorax. The abdomen is shiny and slightly leathery in appearance, with visible dimples (sigilla) where muscles attach. Females have a significantly more robust abdomen than males.
Size Estimate
Body length is typically 6-10 mm for females and 4-6 mm for males. Including leg span, they can reach 20-30 mm. This specimen appears to be an adult female based on the distended abdomen.
Coloration & Markings
Deep purplish-brown to nearly black base color. A distinctive pale, crescent-shaped band (medial band) is present on the anterior of the abdomen, along with a series of lighter triangulated spots or chevrons along the midline. Unlike true Black Widows, it lacks a red hourglass.
Web Type
Builds a messy, irregular 'cobweb' or 'tangle-web' consisting of sticky silken threads. It is usually placed in dark corners, under furniture, or in crevices.
Eye Arrangement
Typical for Theridiids: Eight eyes in two rows of four. The eyes are small and usually dark, though the lateral eyes are often touching.
Leg Characteristics
Legs are relatively long and slender, typically dark brown or reddish-brown without distinct banding. The fourth pair of legs possesses a specialized row of serrated bristles used to comb silk over prey.
Venom & Safety Information
Venom Information
Neurotoxic venom, similar in composition to Latrodectus (true widows) but significantly less potent. It is not considered life-threatening to healthy humans.
Medical Significance
Moderate danger level. A bite (steatodism) may cause localized pain, redness, swelling, and occasionally mild systemic symptoms like nausea or lethargy. Symptoms typically resolve within 24-48 hours. Medical attention is rarely needed unless an allergic reaction occurs.
Safety Recommendations
To avoid bites, wear gloves when cleaning dark storage areas. If found, relocate using the cup-and-paper method to a garage or outdoor shed. Bites should be cleaned with soap and water; apply a cold pack for pain.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found throughout Europe, North America, and Australasia. It is highly synanthropic, preferring dark, sheltered areas inside homes, garages, basements, and sheds.
Behavior & Temperament
Sedentary, nocturnal, and generally timid. It spends most of its time in its web. If disturbed, it usually retreats into a crevice or drops from its web rather than biting. Aggression is extremely low.
Diet & Prey
Insects such as flies, moths, and beetles, as well as other spiders including true Black Widows. They use their silk to entangle prey before delivering a paralyzing bite.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though most frequent sightings occur in late summer and autumn during mating searches.
Description
Steatoda grossa is the most famous of the 'False Widows,' often mistaken for its more dangerous cousins. With its sleek, dark, grape-like abdomen and preference for quiet household corners, it is a master of the shadows and an effective natural pest controller.
Key Features
Large globose abdomen, dark purplish-brown coloration, pale anterior crescent mark, no red hourglass, and irregular tangle-web.
Similar Species
Latrodectus mactans (Black Widow) - distinguish by red hourglass; Steatoda nobilis (Noble False Widow) - distinguish by 'skull' pattern on abdomen; Steatoda borealis - smaller with more pronounced midline marking.
Life Cycle
Females can live up to 6 years and produce several round, white or cream-colored papery egg sacs throughout the year. Spiderlings are translucent and disperse via ballooning.
Ecological Importance
Critical household predator that controls populations of flies, cockroaches, and even other spiders, contributing significantly to indoor pest management.
Conservation Status
Not evaluated by IUCN, but populations are stable and widespread due to their success in human-altered environments.
Interesting Facts
The venom of S. grossa has been studied for its ability to treat Black Widow bites (cross-reactivity), and they are known to actively hunt and displace more venomous spider species in the home.
Photography Tips
Focus on the dorsal (top) side of the abdomen to capture the crescent marking. Use a light source (flashlight) to highlight the shiny texture and dimples, which are diagnostic for this genus.
Identified: 2026-05-25T16:17:52.311563