False Black Widow, Cobweb Spider, Cupboard Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
The specimen features a glossy, globular, bulbous abdomen characteristic of comb-footed spiders, paired with a smaller cephalothorax. The exoskeleton appears smooth and shiny with a polished, leather-like texture. The body proportions show a massive, rounded abdomen dominating the overall mass, typical of well-fed or gravid females within the genus.
Size Estimate
Body length is approximately 6 to 10 millimeters, with a leg span reaching around 15 to 20 millimeters. This appears to be an adult or near-adult female specimen, given the robust, bulbous abdominal dimensions.
Coloration & Markings
Deep dark brown to purplish-black base coloration with subtle lighter pale or yellowish-gray geometric markings and crescent shapes on the dorsal surface of the abdomen. The shiny chitin gives off a subtle metallic or satin sheen under direct light.
Web Type
Irregular tangle web, commonly known as a cobweb. Constructed in dark, undisturbed corners near ground level, consisting of sticky, haphazardly arranged silk threads designed to trip walking insects.
Eye Arrangement
Eight small eyes arranged in two rows of four, typical of the Theridiidae family, positioned closely together on the anterior portion of the cephalothorax.
Leg Characteristics
Relatively slender, moderately long legs featuring subtle darker banding. The legs lack heavy spination but possess comb-like serrated bristles on the tarsus of the fourth pair of legs characteristic of theridiids for pulling silk.
Venom & Safety Information
Venom Information
Contains neurotoxic components (alpha-latrotoxin-like proteins, though less potent than true widows). Envenomation can cause localized pain, redness, and mild systemic symptoms in sensitive individuals.
Medical Significance
Minor medical significance. While bites can be painful and occasionally produce localized blistering, malaise, or fever lasting a few days, they are not life-threatening and do not cause necrotic wounds.
Safety Recommendations
Avoid handling bare-handed. If found inside, gently capture under a glass and release outdoors, or leave undisturbed in a low-traffic area for natural pest control.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution globally. Highly synanthropic, commonly found inside human dwellings, basements, garages, under furniture, and in dark crevices, as well as outdoors beneath rocks, logs, and bark.
Behavior & Temperament
Docile, shy, and non-aggressive. It typically retreats, curls into a defensive ball, or drops from its web when disturbed, only biting as an absolute last resort if trapped directly against skin.
Diet & Prey
Generalist predator feeding primarily on crawling household insects, woodlice, beetles, cockroaches, and occasionally other spiders or small invertebrates caught in its cobweb.
Seasonal Activity
Active year-round indoors, with peak visibility and wandering activity occurring during late summer and autumn months as males actively search for mates.
Description
The False Black Widow is a frequent indoor companion often mistaken for its dangerous relative, the true black widow, due to its dark, bulbous physique. Despite this, it is a harmless and beneficial pest controller quietly managing insect populations in neglected corners of homes and outbuildings.
Key Features
Glossy bulbous abdomen, dark reddish-brown to purplish-black coloration, absence of a bright red hourglass marking, and preference for low-to-the-ground irregular cobwebs.
Similar Species
True Black Widow (Latrodectus spp.), which features a distinct red hourglass marking and lacks the pale geometric dorsal patterns typical of Steatoda grossa.
Life Cycle
Females produce tough, pear-shaped silken egg sacs containing hundreds of eggs. Spiderlings disperse via ballooning or crawling after hatching, undergoing multiple molts to reach maturity over a multi-year lifespan.
Ecological Importance
Acts as an effective natural pest controller in domestic and semi-wild environments, helping to suppress populations of crawling household pests and insects.
Conservation Status
Not evaluated by the IUCN, but highly secure and flourishing globally due to its close association with human habitations.
Interesting Facts
Despite the intimidating common name, Steatoda grossa is remarkably timid and has been known to successfully prey on true black widows that wander into its territory.
Photography Tips
Use macro lenses with diffused lighting to capture the glossy texture of the cephalothorax and abdomen without harsh reflective glare, shooting from a side profile angle.
Identified: 2026-09-28T04:13:06.630800