False Black Widow, Cobweb Spider, Cupboard Spider
Steatoda grossa
Family Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider has a bulbous, globular abdomen and a smaller, oval cephalothorax. The body texture is generally smooth and shiny with fine hairs, characteristic of cobweb spiders.
Size Estimate
Body length ranges from 6 to 10.5 mm for females and 4 to 6 mm for males, with a total leg span reaching up to 20 to 30 mm. The specimen appears to be an adult or sub-adult.
Coloration & Markings
Deep purple-brown to blackish base coloration with pale yellowish or greyish markings, often featuring crescent or triangular shapes on the dorsal abdomen.
Web Type
Irregular tangle web (cobweb) constructed in dark, protected corners, crevices, or near ground level.
Eye Arrangement
Eight eyes arranged in two transverse rows of four, typical of the Theridiidae family, with lateral eyes often touching.
Leg Characteristics
Long, slender legs with subtle banding and lack of prominent spines, typically held flat against surfaces within their web.
Venom & Safety Information
Venom Information
Contains neurotoxic components (latrotoxin-like), but generally mild in potency relative to humans and not life-threatening.
Medical Significance
Minor medical significance; a bite may cause localized pain, redness, and mild swelling, occasionally resembling a minor bee sting.
Safety Recommendations
Avoid handling with bare hands; if relocation is necessary, use a glass and a piece of card to safely move the spider outside.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, frequently found indoors in human dwellings, garages, basements, and outdoors under rocks, logs, and bark.
Behavior & Temperament
Docile and non-aggressive; retreats when disturbed and only bites if firmly pressed against human skin.
Diet & Prey
Insects and other spiders, including crawling pests like beetles, cockroaches, and occasionally other venomous spiders.
Seasonal Activity
Active year-round indoors, with peak mating and wandering activity typically occurring during late summer and autumn.
Description
The False Black Widow is a common household guest often mistaken for the true black widow due to its dark, glossy, and globular body. Despite this resemblance, it is a shy, beneficial predator that helps control indoor pest populations.
Key Features
Glossy bulbous abdomen, dark brownish-purple coloration with pale geometric markings, and the absence of a red hourglass shape.
Similar Species
Latrodectus species (True Widow Spiders), which possess the characteristic red hourglass and lack the pale dorsal markings of Steatoda grossa.
Life Cycle
Females produce spherical silk egg sacs containing up to several hundred eggs, which hatch into spiderlings that disperse via ballooning or crawling.
Ecological Importance
Acts as an effective natural pest controller in domestic and semi-natural environments, regulating insect populations.
Conservation Status
Not evaluated by the IUCN, but highly secure and widespread globally as a synanthropic species.
Interesting Facts
False black widows have been known to successfully prey on true black widows by invading their webs and wrapping them in silk.
Photography Tips
Use macro lenses with good side-lighting to highlight the glossy texture of the abdomen and any faint geometric patterns.
Identified: 2026-10-02T11:35:49.940080