False widow spiders: What are they?

False widow spider infestations have closed several schools in Newham. Pic: The Natural History Muse

False widow spider infestations have closed several schools in Newham. Pic: The Natural History Museum - Credit: The Natural History Museum / Tru

Five schools in Newham have closed as a result of a confirmed or suspected false widow spider outbreak.

But what exactly are false widow spiders, and are they dangerous?

According to the British Arachnological Society, there are three types of false widow spiders in Britain - the noble false widow, or steatoda nobilis, the steatoda bipunctata and the steatodo grossa.

All can be identified by shiny abdomens with a white half moon shape at the front, and are generally between seven and 14 mm long.

The noble false widow has the most toxic bite of any British spider, but there are few confirmed cases of biting and none of serious injury.

The bites are compared to a wasp sting, with a relatively short-lived pain and the possibility of feeling unwell for a day or two.

Serious problems usually only arise if the bite becomes infected or the person’s immune system is weak from other health issues, and anyone with swelling after a spider bite should seek medical advice immediately.

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The spider is native to the Canary Islands and Madeira and was likely imported into the UK with bananas. The first reported sighting was near Torquay in 1879.

False widow spiders are more likely to be found in the southern half of the UK.

Adult males are most commonly found between July and November, while adult females can be found throughout the year.

They lay eggs in a small white sac close to the web, with the baby spiders hatching after two to four months.

An RSPCA spokeswoman said: “The RSPCA advises people to keep their distance from all unusual looking spiders, and that if they want to identify any spider they should contact the British Arachnological Society or the Natural History Museum.

“Any concerns about human welfare should be directed at the environmental health departments or in serious cases to the police as the RSPCA exists to look after animal welfare and does not have expertise in these areas.”

For more information on false widow spiders, visit britishspiders.org.uk/false_widows