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False widow spiders: FAQs


WebMD Medical Reference
Medically Reviewed by Dr Rob Hicks
false widow spider

The false widow spider is the most venomous spider in the UK.

There have been reports of adults and children needing treatment after being bitten by the spiders.

There are a growing number of cases of bites attributed to false widow spiders, which are becoming more common after being accidentally imported during the 19th century.

Read our FAQs to find out how common they are and whether their bite is a threat to health.

What are false widow spiders?

False widow spiders belong to the genus Steatoda. Reports of people being bitten are attributed to Steatoda nobilis, otherwise known as 'the noble false widow'.

There are two other types of false widows: Steatoda bipunctata, Steatoda grossa.

All have globular shaped bodies and their name derives from the fact that they are commonly mistaken for black widow spiders which are in a different genus (Lactrodectus), but the same family (Theridiidae).

Steatoda nobilis is one of the largest with a maximum body length of 14mm for females and 10mm for males.

Are they native to the UK?

Steatoda nobilis is not native to the UK and was accidentally introduced more than 100 years ago from the Canary and Madeira islands, probably among crates of imported fruit. It was first recorded at Torquay, Devon in 1879.

From an initial foothold in the extreme south of England, over the last 25 years it has increased its foothold and has been recorded as far north as Norfolk, Wales and Lincolnshire.

The Natural History Museum says noble false widows are most commonly found in and around domestic and commercial premises and usually make their webs a good height off the ground on external walls of houses and outbuildings.

How bad is its bite?

The false widow is believed to be the UK’s most venomous spider. Bites, though, are rare and usually result from handling the spider roughly or from a spider being trapped between clothing and skin.

However, the British Arachnological Society says it is difficult to obtain accurate evidence as those complaining of bites often do not see the spider but assume they are the culprit because of the absence of a bee or wasp. Alternatively, they only get a brief glimpse.

The effect of a bite is unlikely to be worse than being stung by a wasp or bee and results in pain, redness and swelling However, more serious health problems have been reported. These are likely to be an exceptional reaction to the venom.

What should I do if I am bitten?

The NHS recommends managing symptoms at home but making sure the bite does not get infected.

If in doubt, or if symptoms worsen, seek medical advice.

How can I avoid getting bitten?

Do not disturb spiders if you can help it. They only bite when they feel threatened.

Reviewed on July 12, 2017

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