A man was left with a 4cm hole in his leg after being ‘bitten by a false widow spider’ while waiting outside an Asda.
Michael Wilkinson, 38, spent two months recovering after suffering "nine out of ten" pain.
He initially thought little of the bite but it began to sting and swell half an hour later - before growing to a hole.
Michael claims he recognised the distinctive markings of a false widow on the spider's back as it scuttled away after biting him.
Confirmed cases of false widow bites in the UK are rare, experts say.
Only the two larger species of false widow, the cupboard spider and the noble false widow, are likely to be able to bite through human skin at all.
Michael, from High Wycombe, said: "I was sat on a wall outside Asda and I flicked a spider off my leg.
"As it ran off into a bush I saw the distinctive white band on the abdomen and recognised it as a false widow.
"Just 40 minutes later I noticed swelling on my leg and a hole appearing in the middle.
"It got bigger and bigger and soon there was pus coming out.
"The pain came later on that day and it got worse and worse - over the next days I had problems walking and couldn't sleep because of it.
"Thankfully I got antibiotics quickly but I was told it could have caused sepsis if it was left untreated.
"I was never that keen on spiders before, but now I always look around to spot the markings."
Michael sat on a wall outside his local Asda taking a phone call when he felt something moving on his leg and brushed it away - and spotted a spider with white markings scuttle off.
Michael didn't know it had bitten him until he noticed his leg begin to swell up.
He said it started off looking like "a big boil" before a hole began to emerge in the centre of the reddened, inflamed skin.
As he went home he kept an eye on the wound, as he began to feel a "throbbing pain".
Two days later the infected bite - which he deduced had come from a false widow spider - was still tender, oozing and also began to bleed.
He claims he also found a spider leg stuck in the hole which he had to use tweezers to remove.
Michael went to his GP and it was confirmed to be infected - then he was prescribed antibiotics and painkillers.
He said: "It was extremely painful - a nine out of ten - and it gave me trouble sleeping.
"If I walked round on it, it would start bleeding or discharge would come out. I kept having to wash my clothes because of it."
Michael wants to warn people to look out for false widow spiders in the UK, and not to underestimate the dangers.
He said: "I was lucky I didn't get sepsis. It could have been life-threatening.
"I never imagined it would happen to me.
"I've seen stories in the news, but you never think anything like that will happen to you - until it does."
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