It started out as an unwanted dinner guest – but this grasshopper has now become an unusual family pet.

Karyn Anthoine, 41, was preparing lunch when the creature hopped out of a bag of salad.

She was initially frightened by the creepy-crawly, but her 15-year-old daughter Marie persuaded her to let her keep it as a pet.

Karyn, from Market Harborough, said: "I was scared when I saw it crawl out of the bag, but my daughter would not let me put it in the garden because it was cold and still snowing.

"She was scared it would freeze to death."

The family had been using the bag of Italian salad from Sainsbury's for three days before the 8cm-long stowaway made itself known.

Karyn thinks it must have been sleeping because of the cold in the refrigerator.

Sainsbury's apologised to Karyn and gave her 4,000 points on her Nectar card – the equivalent of about £20.

She said: "I was feeling quite sick for the first few days, knowing we'd been eating salad from the same bag for that amount of time."

Marie, who has ambitions to be a vet, has kept the grasshopper in an insect tank in her room, out of view of her mother, since the family found the creature last week.

Initially, Marie named the bug Jiminy Cricket, after the character in Walt Disney's Pinocchio, but after discovering the insect was a female following some internet research, she was forced to give her a name change.

Karyn said: "We found out she is a female Egyptian grasshopper. So we have changed her name to Isis, after the Egyptian goddess."

Female Egyptian grasshoppers grow to around 6.5cm, so Isis is a particularly large specimen at 8cm long.

Helen Ikin, the grasshopper recorder for Leicestershire Entomological Society, said: "It's not exactly common for people to find them, but if something is found in food that has travelled from that part of the world it is usually an Egyptian grasshopper.

"A lot of people do keep them as pets. They are lovely creatures."

Mrs Ikin said that the females were especially trouble-free as they did not stridulate – make the purring noise with their legs – unlike the male.

Karyn, a psychology teacher, was worried about any restrictions about keeping such an exotic pet in the UK.

But a spokesman for Defra said that an offence would have probably only occurred if Ms Anthoine had released Isis into the wild.

A Sainsbury's spokesman said: "It's really important to us to make sure everything we sell is safe, and we set the highest standards to ensure that this is the case.

"Incidents such as this are very rare, and we take them very seriously indeed. We've contacted the supplier of the salad, who is investigating how this has happened."