False widow spiders - how dangerous are they?

A school has been closed because of an infestation of venomous false widow spiders, and experts say they are on the increase. But how much of a threat do they really pose?

Sightings of the false widow spider, said to be Britain's most venomous, are on the rise and they are spreading.

The species came to the UK in the 1870s and populations have grown since then.

But experts say the species is not usually aggressive towards humans and that being bitten is rare.

'Not aggressive'

John Tweddle from the life sciences department at the Natural History Museum in London said: "Although adult female false widow spiders are certainly capable of biting humans if handled without due care - the smaller males are not known to cause bites."

"It is not an aggressive species towards humans and is most likely to bite when accidentally prodded or squashed, or trapped in clothing."

He also says that now is the time of year we're most likely to notice spiders, because they're at their biggest: "This is when many of the UK's larger species reach maximum size, so are most visible."

Symptoms

If a false widow does bite, it can be pretty uncomfortable.

The symptoms of a bite range from feelings of numbness, severe swelling and discomfort, to various levels of burning or chest pains.

The seriousness of the symptoms depends on the amount of venom that was injected.

There have been no reported deaths from its bite in the UK and experts advise that it's not something to get too worried about - they're no more painful than the sting of a bee or a wasp.