False Black Widow, Cupboard Spider, Bitten Baby Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family trait: comb-like hairs on the fourth pair of legs for silk manipulation.
Physical Description
A medium-sized spider with a bulbous, globose abdomen and a smaller cephalothorax. The body is relatively smooth and shiny, lacking the dense hair of wolf spiders. Females have a larger, more rounded abdomen, while males are smaller and more slender.
Size Estimate
Body length 6-10 mm for females; leg span approximately 25-30 mm. This appears to be an adult female based on the abdominal volume.
Coloration & Markings
Dark purple-brown to blackish-brown base. It typically features a pale, crescent-shaped band on the anterior portion of the abdomen. Some specimens also show light-colored spots or a faint 'V' shape dorsal pattern.
Web Type
Tangle web or cobweb. A messy, irregular three-dimensional structure of sticky silk, usually placed in dark corners, cupboards, under furniture, or in basements.
Eye Arrangement
Eight eyes in two horizontal rows. They are small and relatively uniform in size, characteristic of the Theridiidae family which relies more on web vibrations than vision.
Leg Characteristics
Slender legs, typically darker than the body or matching. They lack heavy spines. The fourth pair of legs features a tarsal comb of serrated bristles used to throw silk over prey.
Venom & Safety Information
Venom Information
Neurotoxic venom, though significantly less potent than the Latrodectus (true widow) genus. Contains latrodectine-like toxins that can cause localized pain and minor systemic symptoms.
Medical Significance
Low to moderate medical significance. Bites are painful and may cause localized swelling, blistering, or malaise. Symptoms (Steatodism) are much milder than Widow bites and rarely require medical intervention.
Safety Recommendations
Use a cup and card for relocation if found indoors. Wear gloves when cleaning out dark storage areas or woodpiles. If bitten, clean with soap and water and use a cold compress.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution across Europe, North America, and Australasia. Highly synanthropic, preferring human dwellings, garages, and sheds.
Behavior & Temperament
Sedentary ambush hunter that stays within its web. It is generally timid and non-aggressive, usually retreating into a crevice when disturbed. Only bites when pressed against skin.
Diet & Prey
Generalist predator eating woodlice, crickets, flies, and even other spiders (including true black widows). It uses high-strength silk to immobilize prey larger than itself.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, with peak mating occurring in summer and autumn.
Description
A common sight in households worldwide, the False Black Widow is an elegant but often misunderstood architect. This spider is most active at night, tending to a chaotic web that serves as an effective biological pest control system for the home.
Key Features
Glossy chocolate-brown color, bulbous abdomen with a crescent-shaped frontal band, and the absence of a red hourglass on the underside.
Similar Species
Latrodectus mactans (Northern Black Widow), which is distinguishable by the red hourglass; Steatoda nobilis (Noble False Widow), which has a more 'skull-like' pattern on its back.
Life Cycle
Females produce round, papery, white-to-cream egg sacs containing 40-100 eggs. They can live up to 6 years, which is quite long for a spider of this size.
Ecological Importance
Critical household predator of invasive pests and disease-carrying insects. They act as a top-tier predator within the micro-ecosystem of building foundations.
Conservation Status
Not evaluated by IUCN, but populations are stable and widespread globally due to their success in human-modified environments.
Interesting Facts
Despite their fearsome appearance, they are known to prey on real Black Widows and are often researched for the proteins in their silk and venom.
Photography Tips
Focus on the dorsal (top) pattern of the abdomen to identify the crescent mark. Use a macro lens or high-zoom under indirect light to avoid the 'glare' off the shiny abdomen.
Identified: 2026-07-05T01:40:01.178606