Frightened allergic woman watches bees swarm in

The postie was glad it happened on a Sunday. Photo / supplied

A swarm of thousands of bees appeared on a Masterton letterbox - outside the home of a woman for whom a single sting could be life-threatening.

Mother-of-four Leah Hemi said the bees appeared on Sunday, a couple of hours after she left for work, while her mother Elaine looked after five young children at the house.

Her mother called to say a swarm of "a couple of thousand" bees had attached themselves to the letterbox at the address the two women share.

"For me it was really quite frightening because I'm allergic - but it was amazing at the same time. It all happened so fast. There was nothing when I left and within two hours there were thousands."

Her mother at first mistook the bees for a "crocheted bag someone put there" but discovered on inspection that the mass was moving and buzzing.

"It got bigger and bigger too in a very short time. They were quite calm though and I only heard them buzzing when I walked up to the letterbox."

Elaine said she closed all the windows because she was unsure if any of the children, aged from 4 to 11, were allergic.

"Leah's throat swells right up when she is stung and we have to take her to the hospital. When she gets stung it's life-threatening. I'm all right but none of the kids have been stung yet, so I was unsure about them."

Her daughter said she called property owner John Mabey, who called in pest destruction.

"The pest guy called two amateur beekeepers, a young couple, because it was honey bees," Mr Mabey said. "They scooped them all up and have combined the swarm with their own hives."

Commercial Masterton beekeeper Denis Watson said honey bee swarms are not uncommon in mid to late spring and a migrant hive in January was notable but not unusual.

"Possibly a queen has failed and what was seen on Sunday was a young queen establishing a new hive," Mr Watson said.