False Black Widow, Cupboard Spider, Dark Comb-Footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded abdomen, comb-like setae on the fourth tarsus used for flinging silk over prey, and building irregular tangle webs.
Physical Description
The spider has a bulbous, globose abdomen and a relatively compact, smooth cephalothorax. The body proportions feature long, slender legs compared to the body size. The abdomen is typically shiny and plump in females, slightly more elongated in males.
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 of roughly 2 to 3 cm. This appears to be an adult specimen due to the well-rounded proportions.
Coloration & Markings
Deep purplish-brown to black or dark charcoal base coloration. Some individuals exhibit faint, pale yellowish or cream-colored markings, chevron patterns, or crescents on the dorsal side of the abdomen, though older females can be entirely dark and glossy.
Web Type
Constructs an irregular, messy tangle web, often referred to as a cobweb, typically built in dark, sheltered corners, crevices, under furniture, or along baseboards.
Eye Arrangement
Eight small eyes arranged in two slightly curved horizontal rows of four, typical of the Theridiidae family, positioned on the front part of the cephalothorax.
Leg Characteristics
Legs are long, slender, and mostly uniform in color with subtle darker banding. They lack prominent spines but possess specialized comb-like claws on the hind tarsi for manipulating web silk.
Venom & Safety Information
Venom Information
Contains neurotoxic components (latrotoxin-like), but the venom is relatively weak compared to true black widows. Bites are typically not medically significant to humans.
Medical Significance
Harmless to humans, though a bite can cause localized pain, redness, and swelling lasting a few hours. In rare cases, minor systemic symptoms like mild malaise may occur. Standard first aid involves cleaning the wound and applying a cold compress.
Safety Recommendations
Avoid handling with bare hands. If relocating from the home, use a cup and a piece of paper to capture the spider and release it safely outdoors.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution, widely found across North America, Europe, Australia, and parts of New Zealand. Prefers indoor habitats, basements, sheds, garages, and dark outdoor crevices near human dwellings.
Behavior & Temperament
Timid, non-aggressive, and nocturnal. When disturbed, they typically retreat quickly into their web or drop to the ground and curl into a ball, only biting if directly trapped or squeezed against skin.
Diet & Prey
Feeds on a wide variety of crawling and flying insects, woodlice, and other spiders. Uses its sticky tangle web to entangle prey before subduing them with venom and wrapping them in silk.
Seasonal Activity
Active year-round indoors, with peak visibility and mating activity occurring during late summer and autumn months as temperatures fluctuate.
Description
The False Black Widow is a frequent household resident that often goes unnoticed in dark corners. With its glossy, bulbous abdomen and preference for untidy tangle webs, it is often mistaken for its dangerous relative, the black widow, but it plays a harmless and beneficial role in controlling household insect populations.
Key Features
Glossy bulbous abdomen, dark purplish-brown to black coloration, irregular tangle web, lack of a red hourglass marking (distinguishing it from Latrodectus species).
Similar Species
Latrodectus species (True Black Widows), which possess a distinct red hourglass or spots on the underside of the abdomen. Steatoda grossa lacks bright red warning colors.
Life Cycle
Females construct tough, brownish silk egg sacs containing up to several hundred eggs. Spiderlings hatch and disperse after molting several times. Lifespan for females can reach several years.
Ecological Importance
Acts as an effective natural pest controller in and around human habitations, helping to keep populations of flies, roaches, and other insects in check.
Conservation Status
Not evaluated by the IUCN, but populations are secure, highly stable, and often expanding due to human habitation and global commerce.
Interesting Facts
Despite their common name, False Black Widows are actually capable of preying on true black widows by carefully invading their webs and subduing them using superior silk-wrapping techniques.
Photography Tips
Use macro lenses with adequate lighting or a ring flash to highlight the glossy texture of the abdomen. Photograph from a slight side angle to capture eye arrangement and leg proportions.
Identified: 2026-09-19T14:35:32.201333