False Black Widow, Cupboard Spider, Comb-footed Spider
Steatoda grossa
Theridiidae (Cobweb Spiders), Order Araneae. Key family traits include a comb-like row of serrated bristles on the tarsus of the fourth leg used for throwing silk.
Physical Description
Features a large, extremely bulbous abdomen and a smaller cephalothorax. The body texture is smooth and glossy. Females (like the one pictured) have a very round, dark abdomen, while males are significantly smaller and more slender.
Size Estimate
Body length 6-10 mm for females, leg span up to 25 mm. This specimen is an adult female, indicated by her size and guarding of an egg sac.
Coloration & Markings
Deep purplish-brown to black overall. Unlike a true widow, it lacks a red hourglass. Common markings include a pale crescent on the anterior of the abdomen and sometimes faint spotting, though mature specimens often appear solid dark.
Web Type
Tangle web or cobweb. A messy, three-dimensional scaffold of sticky silk, typically built in corners, crevices, or under furniture.
Eye Arrangement
8 eyes in two rows of four. The eye pattern is common for Theridiids, appearing as small white/silver pearls against the dark cephalothorax.
Leg Characteristics
Relatively long, thin, and tapered. Lacks heavy spines. Deep brown or black, matching the body color. The fourth pair of legs is equipped with the diagnostic 'comb' for prey wrapping.
Venom & Safety Information
Venom Information
Contains 'alpha-latroitoxin-like' components. While potent against insects, it is significantly less toxic to humans than true Latrodectus (widow) venom.
Medical Significance
Low to moderate clinical importance. Bites may cause localized pain, swelling, and occasionally 'steatodism' (mild nausea and lethargy), but are not considered life-threatening.
Safety Recommendations
If relocation is desired, use a jar and stiff paper to move it outside. Wear gloves when cleaning dark corners or moving stored items to avoid defensive nips.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution; found worldwide. Highly synanthropic, preferring dark, undisturbed areas in homes, garages, basements, and sheds.
Behavior & Temperament
Sedentary ambush hunter. Generally shy and non-aggressive toward humans, preferring to retreat into a crevice or drop from the web if disturbed.
Diet & Prey
Insects (flies, beetles, cockroaches) and other spiders. They are capable of taking down larger prey by throwing sticky silk from a distance until the victim is immobilized.
Seasonal Activity
Active year-round in indoor environments, though most frequent sightings of females with egg sacs occur in late summer and autumn.
Description
The False Black Widow is a common household spider frequently mistaken for more dangerous relatives. This dark, glossy orb-weaver relative is a master of the basement, spinning tangled webs to snag crawling pests. The presence of her round, cotton-like egg sac suggests a well-established resident taking advantage of a sheltered environment.
Key Features
Glossy bulbous abdomen, dark chocolate/purple-black color, lack of red hourglass, and the production of a white, fluffy egg sac.
Similar Species
Latrodectus species (True Black Widows), which have a red hourglass and more charcoal-black color; Steatoda borealis, which has a distinct white line down the center of the abdomen.
Life Cycle
Females produce round to oval egg sacs (visible in the photo) containing 40-100 eggs. These are often white or off-white. Lifespan for females can reach 6 years.
Ecological Importance
Highly beneficial for indoor pest control, as they actively hunt cockroaches, flies, and silverfish that may enter human dwellings.
Conservation Status
Not evaluated by IUCN, but populations are stable and widespread globally due to human habitation.
Interesting Facts
Despite their similar appearance to widows, they are known to occasionally prey upon true black widows. They have also been used in some laboratory studies as a surrogate for widow research.
Photography Tips
Focus on the abdomen to check for the absence of red markings. Side or underbelly shots are best to provide positive identification vs. true widows.
Identified: 2026-07-19T03:14:49.327694