False Black Widow, Cupboard Spider, Bitten Spider
Steatoda grossa
Family Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A bulbous spider with a glossy, pear-shaped abdomen and a smaller cephalothorax. The surface is smooth and shiny, lacks the thick hairs of wolf spiders, and represents the classic 'cobweb spider' physique. In females, the abdomen is significantly larger than the front body segment.
Size Estimate
Body length 6–10.5 mm (females); leg span approximately 20–30 mm. This specimen appears to be an adult or sub-adult female based on the abdominal proportions.
Coloration & Markings
Dark brown to purplish-black base color. Typically features a pale, crescent-shaped band on the anterior portion of the abdomen (facing the head) and faint, triangular or chevron-shaped spots along the midline. Unlike the true Black Widow, it lacks a red hourglass.
Web Type
Tangle web or 'cobweb.' A messy, three-dimensional scaffold of sticky silk often built in corners, cupboards, or under furniture. It lacks the geometric symmetry of an orb web.
Eye Arrangement
Eight eyes arranged in two rows of four. The arrangement is compact, typical of the Theridiidae family, helping them detect vibrations in their tangled webs.
Leg Characteristics
Relatively long and slender legs compared to the body. Legs are usually the same dark color as the body, lacking distinct banding, and are held in a somewhat hunched position when the spider is at rest in its web.
Venom & Safety Information
Venom Information
Neurotoxic venom, though significantly less potent than true Latrodectus (Widow) species. The venom contains alpha-latrotoxin which can affect the nervous system.
Medical Significance
Low to moderate danger. While bites can cause 'steatodism' (local pain, swelling, blistering, and occasionally malaise or nausea), symptoms are generally minor and self-limiting. No known fatalities.
Safety Recommendations
Use gloves when cleaning out cluttered basements or cupboards. If a bite occurs, clean with soap and water and apply a cold compress. Seek medical attention if systemic symptoms (nausea, severe cramping) develop.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Prefers man-made structures, including crawl spaces, basements, cupboards, and sheds. In nature, they live in rock crevices or hollow logs.
Behavior & Temperament
Sedentary and non-aggressive. They spend most of their lives in their webs waiting for prey. If disturbed, they typically retreat to a corner or drop from the web and play dead (thanatosis).
Diet & Prey
Generalist predator feeding on woodlice, crickets, beetles, flies, and even other spiders (including true Widows). They use sticky 'gumfoot' lines in their web to snag crawling insects.
Seasonal Activity
Active year-round in temperature-controlled indoor environments. Outdoors, they are most visible in late summer and autumn during the mating season.
Description
The False Black Widow is a common household resident often mistaken for its more dangerous relative. With its glossy, dark, deep-purple or brown body, it is a master of the shadows, cleaning up household pests from the safety of its tangled web. It is a slow-moving, docile creature that provides excellent free pest control for homeowners.
Key Features
Glossy bulbous abdomen, dark chocolate/purplish color, pale crescent marking on the front of the abdomen, absence of red hourglass marking.
Similar Species
Latrodectus mactans (Northern Black Widow) - Distinguished by the red hourglass; Steatoda nobilis (Noble False Widow) - Distinguished by a more ornate 'skull' pattern on the abdomen.
Life Cycle
Females can live up to 6 years. They produce round, papery, white-to-cream colored egg sacs containing 40-100 eggs. Spiderlings emerge and may disperse via ballooning.
Ecological Importance
Significant household predator. They act as natural pest control, keeping populations of cockroaches, flies, and woodlice in check and contributing to the biodiversity of the 'indoor biome.'
Conservation Status
Not evaluated by the IUCN; however, they are a highly successful, widespread species with stable populations and are considered invasive in some regions.
Interesting Facts
The venom is similar enough to the Black Widow's that antivenom for Latrodectus has been successfully used to treat severe Steatoda bites in the past. They are also known to prey on much larger spiders.
Photography Tips
Focus on the dorsal (top) pattern of the abdomen to identify the specific crescent markings. Use a macro lens or 'portrait' mode with side-lighting to highlight the glossy texture of the cephalothorax.
Identified: 2026-06-15T01:41:17.247132