Steatoda

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Steatoda Temporal range: Palaeogene–present PreꞒ Ꞓ O S D C P T J K Pg N
Female Steatoda bipunctata
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Class:	Arachnida
Order:	Araneae
Infraorder:	Araneomorphae
Family:	Theridiidae
Genus:	Steatoda Sundevall, 1833[1]
Species
See text.
Diversity[1]
120 species

The spider genus Steatoda, in the family Theridiidae, includes about 120 recognized species, distributed around the world (including many cosmopolitan species which are found among human populations worldwide).^[2] One common name is cupboard spider, for many species build their webs in dark, sheltered, undisturbed places around the house or garden, in sheds and garages, under garden, in compost bins, and the like. Signs of the cupboard spider include small white spots of spider droppings, like small splashes of paint, on the floor underneath the web.^[3]

Many spiders of the genus Steatoda are often mistaken for widow spiders (Latrodectus), and are known as false widows. The two genera are closely related – both occurring in the same family, Theridiidae – but Steatoda are significantly less harmful to humans. Not all Steatoda species resemble black widows – they come in many different colors and sizes, mostly smaller than Latrodectus species. Steatoda paykulliana can grow larger than the black widow, and Steatoda castanea looks more like a brown widow.

The colour can range from sandy pale brown to reddish plum to satiny black. Like most spiders, its cephalothorax is smaller than its abdomen, which is somewhat egg-shaped, and can have white or beige to orange markings. Although sometimes not or partially visible, these markings usually consists of a frontal crescent, often with a dorsal line or triangular shapes or both. Orange to reddish-marked Steatoda paykulliana can be mistaken for the redback spider).

In common with other members of the family Theridiidae, Steatoda construct a tangled web, i.e., an irregular tangle of sticky silken fibers. These spiders have very poor eyesight and depend mostly on vibrations reaching them through their webs to orient themselves to prey or to warn them of larger animals that could injure or kill them.

• 
  The eye arrangement of spiders in the genus Steatoda
• 
  Steatoda paykulliana
• 
  Steatoda nobilis
• 
  Steatoda grossa
• 
  Steatoda castanea

As of May 2024^[update], the World Spider Catalog accepted the following extant species:^[1]

Those commonly mistaken for widows include:

• S. borealis. A common species in North America, often mistaken for the black widow (despite being smaller and having colored markings on the dorsal side of the abdomen, rather than the ventral side).
• S. capensis, the black cobweb or false katipo spider. It originates in South Africa, and is found in Australia and New Zealand; in the latter location it is often confused with the katipō spider.
• S. grossa, often known as the cupboard spider. A dark-colored spider which resembles specimens of Latrodectus, though without the characteristic red hourglass marks found on most widow spiders. Bites by S. grossa are rare but painful. Originally from Europe, but now found worldwide.^[4]
• S. nobilis. This spider, a native of the Canary Islands, has since been introduced into the United Kingdom and across Europe. ^[5] and sensationalized stories about the bite of Steatoda nobilis have featured in UK newspaper articles.^[6][7] Its bite is reported to be painful, but normally no worse than a wasp sting, ^[8]
• S. paykulliana, another spider which is often confused with Latrodectus. This one is generally found in the range of Latrodectus tredecimguttatus and is frequently confused with it. Has a medically significant (but not serious) bite.

Other notable and recognizable species in the genus include:

• S. bipunctata. A common house spider in Europe.
• S. triangulosa, the triangulate cobweb spider, a common household spider noted for a pattern of triangles on the dorsal side of its abdomen. Not known to bite; found worldwide.
• S. hespera, the western bud spider. This species is commonly found in the western United States and Canada, where it is an effective predator of the hobo spider. It is often confused with the black widow, despite being significantly smaller (7 to 8 mm) and having no bright-colored markings. Not known to bite humans, but has a venom which is similar to S. paykulliana (a medically significant spider of this genus).

Steatoda is known to prey on other spiders (including true black widows), crickets, ladybugs, cockroaches, and woodlice.^[9]

Some members of this genus do have bites which are reported to have generalized symptoms in humans (such as S. grossa and S. nobilis).^[10] However total number of cases are rare with one ever in France and England each, and 5 in Ireland. A review by Isbister noted 23 over 3 years in Australia. No bites require medical treatment. However, bites by Steatoda species generally do not have any long-lasting effects. Symptoms can include moderate to severe pain increasing for the first hour (without severe sweating).^[10] Some people have reported mild to moderate nausea, headache, and lethargy.^[11] The duration of all symptoms and effects can range from 1 to 60 hours.^[12][13]

The symptoms associated with the bite of several Steatoda species have been named steatodism; and have been described as a less-severe form of latrodectism (the symptoms associated with a widow spider bite). The redback spider antivenom has been thought to be effective at treating bites from S. grossa, after it was mistakenly administered to a S. grossa bite victim who was erroneously believed to have been bitten by the far more dangerous redback. (While the redback antivenom appears clinically active against arachnidism caused by Steatoda spiders,^{[68][100][101][102]} as these cases are often mild and the evidence of its effectiveness is limited, this treatment is not recommended.)^[90]

They are not aggressive, and most injuries to humans are due to defensive bites delivered when a spider gets unintentionally squeezed or pinched somehow. It is possible that some bites result when a spider mistakes a finger thrust into its web for its normal prey, but ordinarily intrusion by any large creature will cause these spiders to flee.

General

• Levi, H.W. (1962). The Spider Genera Steatoda and Enoplognatha in America (Araneae, Theridiidae). Psyche 69:11-36. PDF (with key to American species)

Wikimedia Commons has media related to Steatoda.

• The World Spider Catalog
• Washington State University: Steatoda Spiders