False Black Widow, Cobweb Spider, Cupboard Spider
Paratachydromia or Steatoda grossa (Common Cobweb Spider / False Black Widow)
Theridiidae (Cobweb Spiders), Order Araneae. Key family characteristics include a rounded abdomen, comb-like serrated bristles on the hind tarsi used to pull silk over prey, and irregular tangle webs.
Physical Description
The spider exhibits a bulbous, globose abdomen and a relatively compact cephalothorax. The body surface is slightly shiny with fine hairs. The abdomen is notably large and rounded, typical of gravid female theridiids, giving it a heavy, robust appearance.
Size Estimate
Body length is approximately 6 to 10 millimeters, with a leg span of roughly 15 to 25 millimeters. This specimen appears to be an adult female.
Coloration & Markings
The coloration features dark brown to purplish-black base tones with pale yellowish or whitish markings forming subtle geometric patterns or chevrons across the dorsal abdomen.
Web Type
Builds an irregular, three-dimensional tangle web, commonly known as a cobweb, typically constructed in dark, sheltered areas close to the ground, near foundations or basements.
Eye Arrangement
Eight small eyes arranged in two slightly curved horizontal rows of four across the front of the cephalothorax, typical of the Theridiidae family.
Leg Characteristics
The legs are moderately long and thin, featuring distinct dark banding or rings along the segments. They lack heavy spination but possess specialized serrated setae on the hind tarsi.
Venom & Safety Information
Venom Information
Possesses mild neurotoxic venom used to subdue invertebrate prey. It is not considered medically significant to humans, though bites can cause localized pain and minor swelling.
Medical Significance
Low medical significance. Bites are rare and usually occur only when the spider is trapped against the skin. Symptoms are typically minor and localized, resolving within a few days without professional medical intervention.
Safety Recommendations
Avoid direct handling with bare hands. If found indoors, it can be safely relocated outside using a cup and a piece of paper. No special pest control measures are typically necessary.
Habitat & Behavior
Habitat & Range
Found globally in temperate regions, frequently associated with human structures such as basements, crawlspaces, sheds, and exterior walls near ground level.
Behavior & Temperament
Generally shy, non-aggressive, and nocturnal. It remains hidden in its web retreat during the day and responds to vibrations by rushing out to subdue prey or retreating if disturbed.
Diet & Prey
Feeds on a wide variety of crawling and flying insects, including ants, woodlice, roaches, and other spiders, using sticky silk threads to immobilize them.
Seasonal Activity
Most active during the warmer spring and summer months, though mature adults can often be found year-round in sheltered indoor or subterranean locations.
Description
This robust cobweb spider is a common nocturnal hunter found frequently around human habitations. With its bulbous abdomen and patterned legs, it thrives in dark, protected microhabitats such as basement corners and exterior foundations, playing a quiet yet effective role in natural pest control.
Key Features
Rounded, bulbous abdomen, distinctive pale geometric markings, banded legs, and association with irregular tangle webs near ground level.
Similar Species
Can be confused with true Black Widows (Latrodectus species), but lacks the distinctive red hourglass marking on the ventral abdomen and displays lighter patterned markings dorsally.
Life Cycle
Females produce papery silk egg sacs containing dozens to hundreds of eggs. Spiderlings disperse via ballooning or crawling after hatching, undergoing multiple molts to reach maturity over a one-to-two-year lifespan.
Ecological Importance
Acts as an effective natural predator of household and garden pests, helping to regulate populations of insects around human structures.
Conservation Status
Not evaluated by the IUCN, as populations are abundant, widespread, and frequently thrive alongside human development.
Interesting Facts
False black widows get their name from their striking physical resemblance to black widows, though their venom is vastly less potent and they pose no serious threat to humans.
Photography Tips
Photograph from a slightly elevated top-down or 45-degree angle to capture dorsal abdominal patterns and leg banding clearly. Use macro settings and diffused lighting to highlight texture without harsh glares.
User Notes
outside of basement
Identified: 2026-09-03T17:21:30.147082