False Black Widow, Cobweb Spider, Cupboard Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The spider has a bulbous, globose abdomen and a relatively compact cephalothorax typical of comb-footed spiders. The body is smooth with sparse fine hairs. Females are noticeably larger and rounder than males, which have leaner abdomens and longer legs.
Size Estimate
Body length ranges from 6 to 10.5 mm for females and 4 to 6 mm for males, with a leg span up to 25 mm.
Coloration & Markings
Deep purple-brown to black coloration, often featuring pale yellowish or cream-colored markings, chevron patterns, or crescents on the dorsal abdomen, though some individuals can appear entirely dark.
Web Type
An irregular, sticky tangle web often constructed in dark, protected corners, crevices, under wooden structures, and near ground level.
Eye Arrangement
Eight small eyes arranged in two slightly curved horizontal rows of four, typical of the Theridiidae family.
Leg Characteristics
Thin, tapering legs without prominent spines, usually matching the body color or slightly lighter, held close to the web structure.
Venom & Safety Information
Venom Information
Contains neurotoxic components (latrotoxin-like, though milder). Envenomation is not life-threatening to humans but can cause moderate localized pain and mild systemic symptoms.
Medical Significance
Minimally medically significant. Bites cause localized burning pain, redness, and sometimes mild malaise, but do not result in the severe necrosis or systemic crisis associated with true widow spiders.
Safety Recommendations
Wear gloves when cleaning out dark, undisturbed areas like woodpiles or under decks. If relocation is necessary, gently guide the spider into a container using a piece of card.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution. Commonly found in human-made habitats such as basements, garages, outbuildings, under wooden decks, and dark corners outdoors.
Behavior & Temperament
Timid, non-aggressive, and nocturnal. They typically retreat when disturbed and only bite if trapped or firmly pressed against human skin.
Diet & Prey
Insects and other spiders, including woodlice, flies, and occasionally other larger arthropods captured in their sticky tangle webs.
Seasonal Activity
Active year-round indoors and in sheltered outdoor locations, with peak mating and web-building activity occurring during the warmer summer and autumn months.
Description
The False Black Widow is a frequent occupant of dark, undisturbed crevices around human habitations. Known for their glossy, globular bodies and chaotic webs, they play a quiet role in controlling household and garden insect populations.
Key Features
Globular, shiny dark abdomen with faint pale markings, lack of a red hourglass shape, and presence of an irregular cobweb in sheltered, dark locations.
Similar Species
True Black Widows (Latrodectus species), which can be distinguished by the prominent red hourglass marking on the underside of the abdomen and a more jet-black, velvety texture.
Life Cycle
Females produce papery silk egg sacs containing up to several hundred eggs. Spiderlings hatch and disperse via ballooning or crawling, molting multiple times to reach maturity over a year.
Ecological Importance
Acts as an effective natural predator of common household and garden insect pests, helping to regulate local invertebrate populations.
Conservation Status
Not evaluated by the IUCN; widespread, stable, and highly adaptable to human environments.
Interesting Facts
Despite their ominous common name, False Black Widows are beneficial pest controllers and will readily prey on other unwanted insects and spiders in the home.
Photography Tips
Use macro lenses with a ring flash or side lighting to capture the subtle pale markings and glossy texture of the abdomen without disturbing the spider in its web.
Identified: 2026-10-07T00:29:47.137298