False Black Widow, Cupboard Spider, Dark Comb-Footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A robust spider with a bulbous, oval-to-globular abdomen and a smaller, slightly flattened cephalothorax. The abdomen is typically smooth and shiny with a satin-like texture, lacking the coarse hair found in some other families. Females have a significantly larger, more rounded abdomen than males.
Size Estimate
Body length: females 6-11mm, males 4-6mm; Leg span: approximately 15-25mm. The specimen in the image appears to be a mature female based on the abdominal volume.
Coloration & Markings
Deep purplish-brown to black base color. It lacks the bright red hourglass of a true Black Widow. Often features a pale, crescent-shaped band on the anterior portion of the abdomen and distinctive lighter spotting or 'dimples' on the dorsal surface.
Web Type
Tangle web or cobweb. It is an irregular, messy-looking scaffold of silk typically constructed in corners, crevices, or under furniture. The silk is notably strong and sticky.
Eye Arrangement
Eight eyes arranged in two rows of four. The eyes are small and typical of the family Theridiidae, where the lateral eyes are often adjacent to one another.
Leg Characteristics
Relatively long and slender compared to the body. They are typically reddish-brown to dark brown, translucent in some light, and lack the heavy spines found on hunting spiders. The fourth pair of legs features a 'comb' of serrated bristles used to wrap prey in silk.
Venom & Safety Information
Venom Information
Neurotoxic venom, similar in composition to Latrodectus (true widows) but much less potent. It contains latrodectine, which affects the nervous system of prey and can cause mild reactions in humans.
Medical Significance
Low to moderate danger. Bites are rare and usually occur only if the spider is pressed against the skin. Symptoms may include localized pain, redness, and occasionally nausea or fatigue (steatodism), but they are not life-threatening. Treatment involves local wound care and ice.
Safety Recommendations
Use a cup and stiff paper to relocate the spider outdoors if it is unwelcome. Wear gloves when cleaning out dark areas like garages or sheds. There is no need for chemical extermination for this species.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, found worldwide. It is a synanthropic species, meaning it is commonly found in and around human dwellings, basements, sheds, and garages, preferring dark, undisturbed corners.
Behavior & Temperament
Sedentary and non-aggressive. They spend most of their time hanging upside down in their webs. They are nocturnal hunters that prefer to retreat into a crevice when disturbed rather than bite.
Diet & Prey
Generalist predators feeding on various crawling insects, including beetles, woodlice, and even other spiders (including true Black Widows). They use 'viscid' silk lines to entangle prey before delivering a paralyzing bite.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though sightings often increase in late summer and autumn during the peak of the mating season.
Description
The False Black Widow is a common household resident often mistaken for its more dangerous relatives. With its dark, glossy body and preference for quiet corners, it acts as a highly effective, natural pest controller within the home environment.
Key Features
Glossy rounded abdomen, purplish-black coloration, lack of red markings, and the presence of a pale crescent on the front of the abdomen.
Similar Species
Latrodectus mactans (Black Widow) - distinguished by the red hourglass; Steatoda nobilis (Noble False Widow) - distinguished by more ornate cream-colored 'skull' patterns on the abdomen.
Life Cycle
Females produce several papery, white-to-cream colored egg sacs throughout the year. Spiderlings emerge and may disperse via ballooning. Females can live up to 6 years, while males have much shorter lifespans.
Ecological Importance
Critical for urban pest management. They regulate populations of basement-dwelling insects and help maintain the balance of micro-fauna within man-made structures.
Conservation Status
Not evaluated by the IUCN. Populations are stable and widespread due to their successful adaptation to human environments.
Interesting Facts
These spiders are known to prey upon larger, medically significant spiders, making them beneficial house guests. They have been documented living for over 18 months without food.
Photography Tips
Focus on the dorsal (top) side of the abdomen to capture identifying spots. Use a flashlight or macro lens to highlight the glossiness and check for the absence of red markings underneath.
Identified: 2026-07-20T06:12:46.990229