False Black Widow, Cobweb Spider, Cupboard Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider has a glossy, bulbous, globular abdomen and a smaller, distinct cephalothorax. The body texture appears smooth and shiny with minimal visible hair. It exhibits moderate sexual dimorphism, with females being significantly larger and more roundly globose than the males.
Size Estimate
Body length ranges typically from 6 to 10.5 mm for females and 4 to 6 mm for males, with a leg span extending up to 25 to 30 mm.
Coloration & Markings
Deep dark blackish-brown to dark purple coloration, occasionally featuring faint pale yellowish or greyish triangular or chevron markings on the dorsal side of the abdomen. Unlike true widows, it completely lacks red or brightly colored hourglass markings.
Web Type
Tangle web or irregular cobweb constructed in dark, sheltered corners, crevices, or near ground level, consisting of sticky, haphazardly arranged silk threads.
Eye Arrangement
Eight small eyes arranged in two rows of four, typical of the theridiid family, with lateral eyes often touching or closely situated.
Leg Characteristics
Moderately long, slender to stout legs without prominent spines, featuring subtle dark banding or uniform dark coloration, often held close to the body in a huddled posture when resting.
Venom & Safety Information
Venom Information
Contains neurotoxic components (latrotoxin-like), though significantly milder than that of true widow spiders (Latrodectus spp.).
Medical Significance
Minimally dangerous to humans. A bite may cause localized pain, redness, and swelling lasting a few hours to a couple of days, sometimes accompanied by mild systemic symptoms like malaise or headache, but lacks long-term medical severity.
Safety Recommendations
Avoid handling with bare hands by wearing gloves during cleanups of dark areas, and safely relocate individuals using a cup and card if found indoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution globally, frequently found in temperate regions. Prefers dark, dry, sheltered microhabitats such as outbuildings, basements, under rocks, bark, and corners of human dwellings.
Behavior & Temperament
Nocturnal and timid; non-aggressive, preferring to retreat, drop to the ground, or play dead when disturbed rather than bite.
Diet & Prey
Generalist insectivore feeding on crawling and flying insects trapped in its cobweb, including woodlice, flies, beetles, and occasionally other spiders.
Seasonal Activity
Active year-round indoors, with peak mating and visibility typically occurring during late summer and autumn.
Description
The False Black Widow is a frequent indoor and outdoor neighbor often mistaken for its more dangerous relatives due to its dark, glossy appearance and bulbous abdomen. Living quietly in corners and crevices, it serves as an effective, harmless controller of household pests.
Key Features
Glossy, bulbous dark abdomen, lack of red markings, irregular cobweb construction, and small, compact stance.
Similar Species
True Black Widow (Latrodectus mactans), distinguished instantly by the presence of a bright red or orange hourglass mark on the underside of the abdomen.
Life Cycle
Females produce brownish silk egg sacs containing up to several hundred eggs, which are guarded in the web. Spiderlings hatch, disperse locally or via ballooning, and mature over the course of a year through multiple molts.
Ecological Importance
Acts as an effective natural predator for regulating populations of household and garden insect pests.
Conservation Status
Not evaluated by the IUCN, but secure, widespread, and highly successful in urbanized environments.
Interesting Facts
Despite being called the False Black Widow, it occasionally preys on true widow spiders by invading their webs and subduing them.
Photography Tips
Use macro lenses with diffused lighting or ring flashes to capture the shiny dorsal texture and subtle markings without disturbing the spider.
User Notes
This is dark black
Identified: 2026-10-08T19:24:12.155249