False Black Widow, Cobweb Spider
Paratestudinaria/Steatoda grossa (likely a cobweb spider in the genus Steatoda)
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded, bulbous abdomen, comb-like setae on the fourth pair of tarsi, and building irregular tangle webs.
Physical Description
The spider has a compact body with a noticeably large, rounded, bulbous abdomen and a smaller cephalothorax. The exoskeleton has a smooth, semi-shiny texture. The proportions show typical theridid morphology with a heavy, bulbous rear end.
Size Estimate
Estimated body length is around 6 to 10 millimeters, with a modest leg span of approximately 20 to 25 millimeters, consistent with an adult or sub-adult female cobweb spider.
Coloration & Markings
Dark brown to grayish-black base coloration. The abdomen shows subtle lighter pale markings or a faint central stripe, lacking the bright red hourglass pattern of true widows.
Web Type
Builds an irregular, messy tangle web, often referred to as a cobweb, typically constructed in dark, sheltered corners, crevices, or along structural edges.
Eye Arrangement
Eight small eyes arranged in two rows of four, typical of the Theridiidae family, clustered closely together on the anterior portion of the cephalothorax.
Leg Characteristics
The legs are relatively thin, moderately long, tapering, and lack prominent spines, featuring subtle darker banding and equipped with specialized comb-like claws on the hind tarsi for pulling silk.
Venom & Safety Information
Venom Information
Contains neurotoxic components typical of steatodism, but it is relatively mild compared to true black widows and rarely poses a serious health risk to humans.
Medical Significance
Low medical significance. Bites are uncommon and typically only occur when the spider is pressed directly against the skin. Symptoms usually resemble a mild bee sting with localized pain and redness.
Safety Recommendations
Avoid direct handling with bare hands. If found indoors, gently relocate using a cup and a piece of card. First aid for bites includes cleaning the area with soap and water and applying a cold compress.
Habitat & Behavior
Habitat & Range
Cosmopolitan distribution found worldwide in temperate and tropical regions. Prefers dark, undisturbed microhabitats around human structures, outbuildings, basements, and garden walls.
Behavior & Temperament
Nocturnal and reclusive, spending most of its time hanging upside down in its web. Timid temperament; prefers to retreat or play dead when disturbed rather than bite.
Diet & Prey
Feeds primarily on crawling and flying insects including flies, beetles, cockroaches, woodlice, and occasionally other spiders trapped in its sticky tangle web.
Seasonal Activity
Active year-round in indoor environments, with peak outdoor visibility and mating occurring during the warm summer and early autumn months.
Description
The False Black Widow is a common nocturnal inhabitant of human-made structures, easily recognized by its glossy, bulbous abdomen and preference for messy corner webs. While frequently mistaken for its more dangerous relatives, it is a shy and largely beneficial predator that helps control household pest populations.
Key Features
Bulbous, rounded dark abdomen, absence of red hourglass markings, association with irregular tangle webs, and shiny brownish-black carapace.
Similar Species
True Black Widow (Latrodectus species), which features a distinct red hourglass or red spots on the underside of the abdomen and a jet-black matte finish.
Life Cycle
Females produce brownish, papery egg sacs containing dozens to hundreds of eggs. Spiderlings disperse via ballooning after hatching. They undergo several molts and can live for several years.
Ecological Importance
Serves as an effective natural pest control agent by reducing populations of crawling insects and flies around human habitations, functioning as an important node in urban and suburban food webs.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and widely distributed globally due to strong adaptability to human environments.
Interesting Facts
Despite the intimidating common name, these spiders are completely harmless to humans in the vast majority of encounters and are exceptionally skilled at subduing prey much larger than themselves.
Photography Tips
Use macro lenses with a high depth of field to capture the shiny texture of the abdomen. Shoot from the side or slightly above while the spider is resting in its web during low-light conditions using a diffused flash.
Identified: 2026-09-16T15:51:20.192159