Cupboard Spider, False Black Widow, False Button Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae
Physical Description
A bulbous, globose abdomen that is significantly larger than the cephalothorax. The surface is smooth, shiny, and relatively hairless. Female abdomens are large and round, while males have a more elongated abdomen and smaller overall body size.
Size Estimate
Females range from 6-10.5 mm in body length; males 4-6 mm. Leg span can reach up to 25-30 mm.
Coloration & Markings
Dark purple-brown to black base color. Juveniles and some adults possess a pale crescent-shaped band on the anterior of the abdomen and distinctive light-colored spots or chevrons on the dorsal surface, though these can fade to solid dark in mature females.
Web Type
Messy, three-dimensional tangle or cobweb. Usually built in dark corners, under furniture, or in cupboards. The silk is notably strong and non-sticky except for 'gumfoot' lines that tether to the ground.
Eye Arrangement
Eight eyes arranged in two rows of four. Most eyes are roughly equal in size, though the anterior medians may be darker. This lateral spacing is characteristic of the Theridiidae family.
Leg Characteristics
Slender, tapering legs. The first pair of legs is usually the longest. Generally the same dark color as the body, sometimes with faint reddish or lighter banding at the joints in lighter specimens.
Venom & Safety Information
Venom Information
Contains various toxins including alpha-latrotoxins, similar to black widows but much less potent. The venom is neurotoxic but lacks the severity of the Latrodectus genus.
Medical Significance
Low to moderate danger. Bites can cause 'steatodism', characterized by localized pain, redness, and occasional nausea or lethargy for a few hours. No long-term damage is expected; symptoms are usually managed with localized cold packs.
Safety Recommendations
If found indoors, they can be easily relocated using a jar and a piece of paper. Wear gloves when cleaning out dark-reaching areas like woodpiles or neglected cupboards to avoid accidental pinches.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Highly synanthropic, preferring human dwellings, garages, basements, and sheds. In nature, they reside under rocks or in tree hollows.
Behavior & Temperament
Sedentary and nocturnal. They typically stay within their web awaiting prey. Extremely timid and non-aggressive; they will usually flee or feign death (thanatosis) if disturbed. Bites only occur if the spider is squeezed against skin.
Diet & Prey
Generalist predators feeding on various insects, including ants, beetles, and crickets. They are even known to prey on other spiders, including much more dangerous species like 'True Black Widows' (Latrodectus).
Seasonal Activity
Year-round in indoor environments. Outdoors, peak activity occurs in late summer and autumn when males wander in search of mates.
Description
The False Black Widow is a common household resident often mistaken for its more dangerous relatives. Possessing a sleek, mahogany-colored body and a penchant for dark corners, it acts as a quiet housekeeper by snagging pests in its sprawling cobweb.
Key Features
Glossy, dark bulbous abdomen; pale crescent mark on the front of the abdomen (often visible in juveniles); lacks the red hourglass marking found on true Black Widows.
Similar Species
Latrodectus mactans (Northern Black Widow), which is distinguished by the red hourglass; Steatoda nobilis (Noble False Widow), which has more ornate, cream-colored markings.
Life Cycle
Females produce several white to off-white, round, papery egg sacs. Spiderlings emerge and may balloon. Adults can live for several years (up to 6 for females), which is a long lifespan for such a small spider.
Ecological Importance
Significant natural pest control in urban environments. They help regulate populations of woodlice, flies, and destructive pantry beetles.
Conservation Status
Not evaluated (Least concern). They are highly adaptable and their population is stable due to their close association with human structures.
Interesting Facts
They are famous for their ability to prey on much larger spiders. They are often called 'Cupboard Spiders' because of their frequency of appearing in dark pantry spaces.
Photography Tips
Focus on the dorsal (top) side of the abdomen to look for the crescent mark. Using a soft flash will highlight the glossy texture of the body and the structure of the messy cobweb.
Identified: 2026-06-02T01:45:58.744627