Steatoda

Sundevall, 1833

False Widow Spiders, Cupboard Spiders

Species Guides

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Steatoda is a of cobweb spiders in the Theridiidae containing approximately 120 recognized with worldwide distribution. Many species are , commonly found in human dwellings, sheds, garages, and undisturbed corners. Members are frequently mistaken for widow spiders (Latrodectus) due to similar body shape and web structure, earning them the "false widows," though they are significantly less harmful to humans. The genus includes both native and , with Steatoda nobilis (Noble False Widow) being particularly notable for its rapid range expansion in Europe and North America.

Steatoda castanea by (c) Miroslav Deml, some rights reserved (CC BY). Used under a CC-BY license.Steatoda albomaculata by (c) Roman, some rights reserved (CC BY), uploaded by Roman. Used under a CC-BY license.Steatoda grossa by (c) David Short, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Steatoda: //stiːəˈtoʊdə//

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Identification

Steatoda are distinguished from the related Latrodectus (true widows) by the absence of the characteristic red hourglass marking on the found in most widow spiders. Steatoda markings, when present, occur on the surface rather than ventral. S. triangulosa is identified by paired wavy rusty or purplish-brown lines on a dirty white or beige abdominal background. S. grossa is dark-colored without red hourglass marks. S. nobilis is relatively large with a brown, bulbous abdomen often marked with cream-colored patterning. Reliable species identification often requires examination of genitalia. Sheetweb weavers (Linyphiidae) can be distinguished by prominent leg setae, which Steatoda lacks.

Images

Habitat

Many Steatoda are strongly , building webs in dark, sheltered, undisturbed locations including cupboards, basements, cellars, garages, sheds, compost bins, and under garden furniture. Some species occupy natural in warmer parts of their range; for example, S. triangulosa lives in natural habitats in the southern Palearctic but is restricted to human-associated environments in colder climates. Webs are typically constructed in protected recesses where the spider can retreat into crevices when disturbed.

Distribution

distribution with approximately 120 recognized worldwide. Native ranges vary by species: S. nobilis originated from Madeira and the Canary Islands; S. grossa is originally European but now worldwide; S. capensis is native to South Africa; S. triangulosa is Palearctic in origin but introduced to North America. Multiple species have been introduced beyond native ranges through human commerce, with S. nobilis showing particularly rapid recent expansion in Western Europe, California, and South America.

Seasonality

Activity patterns vary by and climate. S. triangulosa mates from late spring through early autumn. In temperate regions, and immatures may overwinter in protected locations. Year-round presence in indoor where conditions remain favorable.

Diet

Known to prey on other spiders (including true black widows), crickets, , , woodlice, and various insects. S. triangulosa has been documented preying on in the southern United States. Prey is captured in tangled, irregular webs and subdued with venom.

Life Cycle

Females deposit in spherical, opaque white sacs. S. triangulosa produces about 30 eggs per sac and may generate six or more sacs in a lifetime. Eggs are visible through the sheer fabric of the sac. Spiderlings emerge from egg sacs and disperse; in captivity, they may require one additional before dispersing. Lifespan in protected indoor conditions may exceed one year, potentially two or more years. Males are generally smaller and more slender with proportionally longer legs.

Behavior

Constructs irregular, tangled cobwebs with sticky silken fibers, often with a more-or-less sheet-like central platform. Hangs upside down in the web. Possesses very poor eyesight and relies primarily on vibrations transmitted through the web to detect prey and threats. Not aggressive; defensive bites occur primarily when spiders are squeezed or pinched. May mistake fingers thrust into webs for prey, but typically flees from large creatures. Some , including S. triangulosa, may build webs in close proximity to other spider species including brown recluses.

Ecological Role

of arthropods including other spiders and various insects. S. hespera in western North America is an effective predator of the hobo spider (Eratigena agrestis). such as S. nobilis and S. capensis may impact native faunas through competition and ; S. capensis shows potential for competitive displacement of the endangered katipō spider (Latrodectus katipo) in New Zealand. S. triangulosa has been evaluated as a potential agent for but deemed unlikely to be effective.

Human Relevance

Frequently encountered in human dwellings due to habits. Bites are rare and generally defensive; most are not dangerously venomous to humans. S. grossa and S. nobilis bites can cause moderate to severe pain increasing for the first hour, with possible mild to moderate nausea, headache, and lethargy; typically resolve within 1-60 hours without long-lasting effects. No bites have required medical treatment. S. paykulliana has a medically significant but not serious bite. The condition caused by Steatoda bites has been termed "steatodism," considered a less-severe form of latrodectism. Media sensationalism, particularly regarding S. nobilis in the UK, has generated public concern disproportionate to actual risk. Some species kept as pets by enthusiasts.

Similar Taxa

Misconceptions

Despite frequent media sensationalism, particularly regarding Steatoda nobilis, bites from this are rarely medically significant and have not required professional medical treatment. The spiders are not aggressive and do not actively seek to bite humans. The "false widow" contributes to inflated risk perception; while related to true widows, Steatoda are significantly less dangerous.

More Details

Invasive Spread

Steatoda nobilis has shown rapid expansion from its native Madeira and Canary Islands, now established across Western Europe, California, and parts of South America. Transport appears linked to ornamental plant trade rather than banana shipments as previously assumed. Climate-matching models predict high invasion risk for South Africa, southern Australia, and New Zealand.

Web Structure

Unlike the stereotypical orb web, Steatoda constructs a three-dimensional tangle of sticky threads with a retreat area. The web accumulates debris including insect and spider droppings (small white spots), which can indicate presence even when the spider is hidden.

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Sources and further reading