A drive to reduce pesticides on fruit has backfired after three mothers found deadly black widow spiders crawling out of bunches of grapes they bought at Tesco.
Black widows, which have distinctive red markings, are potentially deadly to humans. Their venom is 15 times more potent than a rattlesnake.
The supermarket group has launched an investigation after the latest incident, when Stephanie Thorneycroft from Wimborne, Dorset, discovered the spider as she was rinsing the grapes at the weekend. Mrs Thorneycroft, a mother of two, said: "I emptied the grapes into a colander, shook them and this black spider came up the side. I screamed."
A neighbour killed the spider and it was taken back to the store in Ferndown, Dorset. Last week Noelle Bolzen, from Southport, Merseyside, found a dead black widow in another bunch of Tesco grapes. In October Linda Cooper, a teacher from Ferndown, Dorset, was picking out grapes from her fridge to put in her children's lunch boxes.
She said: "A black shiny spider the size of a thumbnail come crawling to the top. It had a red hourglass shape on its abdomen. I called the police." That spider was captured and donated to London Zoo, where it is on public display.
A Tesco spokesman said the group could not explain why the spiders had been discovered in Californian grapes. "All the grapes should be rigorously checked."
He said they were from a range called Nature's Choice, aimed at reducing pesticide levels in response to consumer pressure to improve its green production techniques.
"Instead of pesticides, we use natural predators - in this case, small, harmless spiders - to prevent insects from puncturing the grapes. But less pesticide means other insects can hide among the fruit without harm. This appears to be what happened with the black widows."
The Food Standards Agency said it would not be taking any action.