- adults of both sexes are usually larger than both Steatoda bipunctata and Steatoda grossa
- epigyne is variable and similar to that of Steatoda grossa
- male palps are also similar to those of Steatoda grossa but are relatively easy to distinguish
- A medium sized species usually well marked with distinctive pattern on abdomen.
- A distinct cream or whitish band around the front of the abdomen is almost always present
- Legs usually red or reddish and usually serves to separate this form other species of Steatoda at a quick glance
Other species of Steatoda and some other larger species of theridiid spider.
Body length (excluding legs):
- Female: 8–15mm
- Male: 7–10mm
- Female: 20–32mm
- Male: 16–22mm
In general, the life cycle lasts about one to two years and the females usually live longer than the smaller males.The white, spherical egg-sacs are produced at intervals, their number depending on the food supply. Eggs hatch within 2-4 months.
Males usually achieve maturity within a single year and die shortly after as they cease to feed once mature.Females achieve maturity within the second year and depending on environmental conditions and sufficient prey may live into the third year.
Mature and reproductive male spiders are found in summer and autumn, mature females can be found all year round and egg sacks are laid from spring through to autumn.
Local dispersal is achieved through ballooning on silk threads. Longer distance dispersal is aided by transportation of goods by road and rail and shipping network.
- Canary Islands
- mainland Europe
- quite rapidly south to London (Surrey) and Berkshire
- while increasing in Essex
- northwards with recent records from Leicestershire and Barry, South Glamorgan.
Steatoda nobilis is strongly synanthropic and is most commonly found in and around domestic and commercial premises, including conservatories, public toilet blocks, garages and sheds.
The false widow spider is afforded no conservation status.
Due to its notoriety as the UK’s most venomous spider Steatoda nobilis may be threatened by remedial pest control.
Steatoda nobilis is currently a colonising species in the UK and has been expanding rapidly since the late 1980’s. The expansion of false widow spider is likely to be in response to increasing temperatures in the UK caused by climate change.
Although this is a colonising species in the UK, it does occupy a somewhat vacant niche and is unlikely to have impact on other species of spider.
Steatoda nobilis is a spider in the genus Steatoda, known in the United Kingdom as the noble false widow and often referred to as the false widow.[a] As the common name indicates, the spider superficially resembles and is frequently confused for the black widow and other spiders in the genus Latrodectus, which can have medically significant venom. Steatoda nobilis is native to Madeira and the Canary Islands from where it allegedly spread to Europe, and arrived in England before 1879, perhaps through cargo sent to Torquay. In England it has a reputation as one of the few local spider species which is capable of inflicting a painful bite to humans, with most bites resulting in symptoms similar to a bee or wasp sting.
Steatoda nobilis has a brown bulbous abdomen with cream coloured markings that are often likened to the shape of a skull. The legs are reddish-orange. Females range in size from about 9.5 to 14 mm in size, while males are 7 to 11 mm. 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.
Distribution, habitat and ecology
The spider is an introduced species across Europe, plus parts of North Africa, and likely spreading. It was found for the first time in 2011 in Cologne, Germany. It is originally from the Canary Islands and Madeira. In England it has been reported mostly in southern counties, but its range appears to be expanding northwards. In 2011, the spider was reported as an established invasive species in the USA, in Ventura County, California.
As with other members of the family Theridiidae, Steatoda nobilis constructs a cobweb which is an irregular tangle of sticky silken fibres. 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. They have poor eyesight and depend mostly on vibrations reaching them through their webs to orientate themselves to prey or warn them of larger animals that could injure or kill them.
Population expansion in UK and Ireland
The distribution of Steatoda nobilis is expected to increase northwards in the UK, due to, at least partly, mild summers in recent years. This prediction was reported by Stuart Hine of the Natural History Museum, and is substantiated by the National Recording Scheme.
The spider is reported to be an established species in Ireland.
Like almost all spiders, Steatoda nobilis is venomous, but its bite is almost exclusively of mild effect on humans, without the severe consequences that can occur with black widow spiders. Its bite is often alleged to be one of the medically significant for humans, even though the few recorded bites do not typically present long-lasting effects. The symptoms of a bite are typically similar to a bee or wasp sting. 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. Only the female spider bites humans.
Sensationalised stories about the bite of Steatoda 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."  Steven Falk, an entomologist, cautioned that without "hard evidence", it is difficult to know how many of the bites reported in the media have been caused by false widow spiders.
- 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 Steatoda nobilis.
- 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 Steatoda nobilis.
- In 2012 a woman in Dorset suffered serious effects after her hand was supposedly bitten by a false widow spider.
- In 2013 a man in Sidcup of London was allegedly bitten in his sleep, reporting that his hand had turned black and yellow. His hand remained swollen for five weeks until doctors gave him a course of antibiotics.
- In October 2013, it was reported that a man from Romford in Essex had been allegedly bitten by a false widow. He was treated for bacterial infection with antibiotics and needed to have his leg drained of pus.
- In October 2013, a British school in the Forest of Dean was closed for a day for fumigation as a result of an outbreak of Steatoda nobilis on the site. 
a. ^ The correct and full English name for Steatoda nobilis is "Noble false widow". Media coverage usually abbreviates this to "false widow", although Steatoda nobilis is strictly speaking one of the false widows. Steatoda grossa and Steatoda paykulliana are other examples of false widow spiders.
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- 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.
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