A bite from a black widow can be fatal

Mr Seal had been warned about black widow spiders during business trips to Florida and he recognised it as a highly-poisonous female.

"I knew there was a potential danger and so immediately cleared the area and called the plant protection office," he said.

Geordie Jackson, an employee at the butterfly farm, said if the spider bit a child or an elderly person the poison could kill them.

"Anyone bitten by a black widow must be sent to a hospital within a hour and injected with an anti-venom to counteract the poison," he said.

An RSPCA spokesperson said: "The workers' sensible precautions saved them from a potentially fatal situation."

Female black widow spiders are deadlier than the males and almost 20 times larger.

The spider will remain on show at the butterfly farm - in a glass case.