Steatoda nobilis is a spider in the genus Steatoda, commonly known in England as the noble false widow^[1][2] (While several species are worldwide known by the imprecise common name 'false widows', this often leads to misunderstandings about identities). As the common name of 'noble false widow' indicates, the spider superficially resembles, and is frequently confused for, the black widow and other venomous spiders in the genus Latrodectus. S. nobilis is native to Madeira and the Canary Islands from where it allegedly spread to Europe,^[3] and arrived in England before 1879, perhaps through bananas sent to Torquay.^[4] In England it has a reputation as one of the few local spider species which is capable of inflicting a painful bite to humans,^[5] although bites are a comparatively rare occurrence and alarmist media reports are often poorly founded.

Description

Females of Steatoda nobilis have a round, bulbous abdomen, with variable pale marbled markings on the dorsum, such as longditudinal light lines, and a light anterior band. Abdomen ventrally dark. Prosoma dorsally dark, fovea as shallow pit. Sternum dark brown. Males tend to have smaller more elongated abdomens, with pale brown legs. and dark brown less patterned abdominal markings. In both sexes, the legs pale yellow-brown. Females range in size from about 9.5 to 14 mm in size, while males are 7 to 11 mm.^[1] Males are able to produce stridulation sounds during courtship, by scraping 10-12 teeth on the abdomen against a file on the rear of the carapace.

Male with swollen pedipalps

Distribution, habitat and ecology

The spider is introduced across Europe, plus parts of North Africa, and likely spreading. It was found for the first time in 2011 in Cologne, Germany.^[6] It is originally from the Canary Islands and Madeira.^[7] In England it has been reported mostly in southern counties,^[8][9] but its range appears to be expanding northwards.^[10][11] It has recently established itself in Ventura County, California.^[12]

As with other members of the family Theridiidae, S. nobilis constructs a cobweb, i.e., an irregular tangle of sticky silken fibres. However, its 'scaffold web' differs from others of the genus in the exceptional strength of the silk, and in the tubular retreat that is at least partly concealed in a deep crack or hole.^[9] They have poor eyesight and depend mostly on vibrations reaching them through their webs to orient themselves to prey or warn them of larger animals that could injure or kill them.

Population expansion in UK

Steatoda nobilis, Hampshire, England

The distribution of S. nobilis is expected to increase northwards in the UK, due at least partly to mild summers in recent years. This prediction was reported by Stuart Hine of the Natural History Museum,^[13] and is substantiated by the National Recording Scheme.^[9]

Medical significance

Female of S. nobilis in Hampshire

S. nobilis in its web in Hampshire

They are not aggressive, so occasional injuries to humans are only likely due to defensive bites delivered when a spider gets unintentionally squeezed or pinched.

The bite of S. nobilis is almost exclusively of mild effect on humans, without severe consequences that can present from black widow spiders. However, its bite is often alleged to be one of the medically significant for humans, even though the few recorded bites do not typically present any long-lasting effects. The bite of this spider, along with others in the genus Steatoda, can produce a set of symptoms known as steatodism. Symptoms of bites include intense pain radiating from the bite site, along with feverishness or general malaise.^[14]

Sensationalized stories about the bite of S. nobilis have featured in UK newspaper articles. Stuart Hine from the Natural History Museum, London responded on the naturenet blog, stating, "Of course I also explain the great value of spiders and how rare the event of spider bite in the UK actually is. I also always explain that up to 12 people die from wasp/bee stings in the UK each year and we do not panic so much about wasps and bees – but this never makes it past editing." ^[13]

Alleged Incidents

• In 2006 a Dorchester man spent three days in Dorset County Hospital with symptoms of heart seizure, after suffering a spider bite believed to be caused by S. nobilis. A spider was observed in the act of biting the man, though it was not captured and so not formally identified by an experienced arachnologist.^[5]
• In 2012 a man collapsed in Southampton after apparently being bitten on his neck. He had complained of feeling hot, queasy and light headed. He required treatment in hospital, where it was discovered that he had been bitten 10 times on the neck, allegedly by the same large spider. The spider (which had been trapped in the victim's hooded jacket) was caught and tentatively identified by health workers as S.nobilis. There is no information about whether the identity was confirmed by an experienced arachnologist, so the identity of the spider is dubious.^[15]
• In 2012 a woman in Dorset suffered serious effects after her hand was supposedly bitten by a false widow spider. The identity of the spider involved, if any, remained uncertain, and there is no direct evidence to show it was actually a spider bite.^[16]

References

1. ^ ^{a b} Snazell, R. and Jones, D. (1993). "The theridiid spider Steatoda nobilis (Thorell, 1875) in Britain". Bulletin British Arachnological Society 9 (5): 164–167. 
2. ^ Jones, D. (1993). "The Return of Steatoda nobilis (Thorell)". Newsletter of the British Arachnological Society 49: 7–8. 
3. ^ Kulczycki, A., Legittimo, C.M., Simeon, E. and Di Pompeo, P. (2012). "New records of Steatoda nobilis (Thorell, 1875) (Araneae, Theridiidae), an introduced species on the Italian mainland and in Sardinia". Bulletin British Arachnological Society 15 (8): 269–272. 
4. ^ Octavius Pickard-Cambridge (1879). "On some new and rare British spiders, with characters of a new genus". Annals and Magazine of Natural History 5 (4): 109–215. 
5. ^ ^{a b} David Sapsted (17 November 2006). "Watch out, the black widow's sister is ready to bite you". Daily Telegraph (London). 
6. ^ "Observation by C Wieczorrek". 15 December 2006. Retrieved 22 November 2012. 
7. ^ "World Distribution Map of S. Nobilis". British Arachnological Society. Sept/Oct 2012. Retrieved 22 Nov 2012. 
8. ^ Harvey, P.R., Nellist, D.R. and M.G. Telfer, ed. (2002). Provisional Atlas of British spiders (Arachnida, Araneae) 1 &2. Huntingdon: Biological Records Centre. 
9. ^ ^{a b c} "Summary for Steatoda nobilis (Araneae)". British Arachnological Society: National Recording Scheme. 2010-2012. Retrieved 22 Nov 2012. 
10. ^ "Biting spider widens its web". BBC News. 2001-09-21. 
11. ^ "Warning over rise in UK's most dangerous spider due to warmer winters". MailOnline. 2 May 2007. 
12. ^ Vetter, R.S. (2012). "A large European combfoot spider, Steatoda nobilis (Thorell, 1875) (Araneae: Theridiidae), newly established in Ventura County, California". The Pan-Pacific Entomologist 88 (1): 92–97. 
13. ^ ^{a b} "The Ranger's Blog: The truth about Steatoda nobilis - is it the UK's most dangerous spider?". 2 May 2007. Retrieved 22 November 2012. 
14. ^ Warrell, D.A., Shaheen, J., Hillyard, P. D. & D. Jones (1991). "Neurotoxic envenoming by an immigrant spider (Steatoda nobilis) in southern England". Toxicon 29 (10): 1263–1265. doi:10.1016/0041-0101(91)90198-Z. PMID 1801319. 
15. ^ "Father collapses after being bitten 10 times by the UK's most venomous spider after it falls into his HOOD". Daily Mail (London). 
16. ^ Luke Salkeld (18 April 2012). "'I nearly lost my hand to Britain's most poisonous spider': Woman bitten while she SLEPT by close relative of deadly Black Widow that lives in UK". Daily Mail. Retrieved 22 November 2012.