False Black Widow, Cupboard Spider, Dark Comb-Footed Spider
Steatoda grossa
Family: Theridiidae (Cobweb Spiders); Order: Araneae
Physical Description
A medium-sized spider with a bulbous, globose abdomen and a smaller, oval cephalothorax. The surface is smooth and glossy, 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: 6-10mm for females; leg span: 15-25mm. The specimen in the image appears to be a mature or near-mature female.
Coloration & Markings
Deep purplish-brown to black. While it lacks the red hourglass of a true Black Widow, it often features a pale crescent-shaped band on the anterior of the abdomen and sometimes light-colored spots or chevrons on the dorsal side.
Web Type
Tangle web or cobweb. These are irregular, messy three-dimensional structures of sticky silk, typically built in corners, under furniture, or in crevices.
Eye Arrangement
Typical Theridiid arrangement: eight eyes in two rows of four, though they are quite small and difficult to see without magnification.
Leg Characteristics
The legs are relatively long and slender, often slightly lighter in color than the body (amber or dark brown). They lack heavy spines but have a 'comb' of serrated bristles on the tarsus of the fourth leg used to wrap prey.
Venom & Safety Information
Venom Information
Neurotoxic venom, though significantly less potent than that of a true Black Widow. It contains latrodectine-like toxins that can cause localized pain and systemic symptoms in humans.
Medical Significance
Moderate significance. Bites are painful and can cause 'steatodism', which includes symptoms like blistering, nausea, and malaise lasting 1-2 days. It is rarely dangerous but should be monitored; seek medical attention if symptoms persist.
Safety Recommendations
Use gloves when moving items in storage or working in crawlspaces. To relocate, use the cup-and-paper method. If bitten, clean the area and apply a cold compress.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide in temperate regions. It is highly synanthropic, preferring dark, sheltered areas inside homes, basements, crawlspaces, and sheds.
Behavior & Temperament
Sedentary and non-aggressive. They spend most of their time waiting in their webs. If disturbed, they usually retreat to a corner or drop on a silk line. They only bite if squeezed or pressed against skin.
Diet & Prey
Generalist predators feeding on various crawling insects, pillbugs, and even other spiders, including true Black Widows. They use sticky silk to entangle and immobilize prey before biting.
Seasonal Activity
Active year-round in temperature-controlled indoor environments, though sightings often increase in autumn as they seek shelter or mates.
Description
An inconspicuous inhabitant of shadowy corners, this glossy dark spider is often mistaken for its more famous cousin. It is a master of low-energy living, thriving in the dark crevices of human dwellings.
Key Features
Glossy bulbous abdomen, dark eggplant/black color, absence of a red hourglass, and an irregular 'cobweb' style web.
Similar Species
Latrodectus species (True Black Widows - have red hourglass), Steatoda nobilis (Noble False Widow - has cream 'skull' pattern), Steatoda borealis.
Life Cycle
Females produce several white, papery egg sacs containing up to 200 eggs each. Spiderlings disperse via ballooning. They can live for several years in stable indoor environments.
Ecological Importance
Highly beneficial for室内 pest control; they consume significant numbers of common household pests and help maintain the balance of the urban indoor ecosystem.
Conservation Status
Not evaluated by IUCN; stable and widespread due to its adaptation to human environments.
Interesting Facts
Steatoda grossa is a known predator of the Redback and Black Widow spiders, making them a natural biological control agent for more dangerous species.
Photography Tips
Focus on the dorsal (top) of the abdomen to capture crescent markings. Use a flashlight or diffuse flash to highlight the glossy texture against the dark body.
User Notes
On a unfinished floor
Identified: 2026-06-03T02:05:37.843680