The unusual properties of the Brazilian Wandering Spider in the trouser department are currently being studied by scientists who are seeking alternatives to Viagra for the treatment of impotence.

But mother-of-two Maria Layton, from Bristol, had more immediate concerns when she unwrapped the bunch of bananas for her six-year-old daughter, Siri. A cocoon attached to the fruit – which had been shipped from Costa Rica – contained Brazilian Wandering Spider eggs. And when the tiny arachnids began to hatch she placed the deadly attachment into a sealed container in the freezer before calling Tesco customer services.

“My husband bought the bananas from Tesco – they had been in the house a whole day before I ripped the bag open,” said 43-year-old Ms Layton, quoted in the Daily Telegraph. “Siri asked for a banana. The first banana had a funny bit on it, so I got another one for her and that was when I found the massive spider cocoon.”

When Ms Layton went online for more information she was terrified by what she discovered. “There was an image which looked very similar to mine,” she said. “I was so scared. I don’t like spiders at the best of times, but have read about the Brazilian Wandering Spiders – and was very scared about the potential threat. The spider cocoon started to unfurl so I put it in the freezer as I read that that is supposed to kill them.”

In rare instances the bite of the spider – also nicknamed the ‘banana spider’ – can also lead to death as well as stonking boners. However, Ms Layton found Tesco customer services less than helpful. They suggested she should bring the yellow fruit and spiders back to the store so that the bar code could be scanned and her money refunded.

“Tesco were a bit useless,” she said. “I was really concerned about the possibility of this dangerous spider and spider eggs in my house and really wanted some helpful advice on how to act. I wasn’t sure if other spiders or eggs had escaped when I ripped the bag open.”

A Tesco spokesperson said: “Our policy is for the customer to take the product to the store, where it can be investigated. We don’t have a service whereby someone can go out to the home.”

This isn’t the first banana skin Tesco has slipped up on. A 50-year-old man recently faced an age-check while buying bananas and nuts in Nottingham for fear he might be planning to ferment the fruit to make alcohol.