Hundreds of fen raft spiders – the largest of the UK’s spider species - have been released into the UK as part of a programme to boost their dwindling numbers, and now zoo staff have been awarded for increasing numbers of this rare arachnid.

The spiders, which can grow as big as a small rodent, have black or brown bodies with white or cream stripes along the sides.

Adult females can span nearly 3 inches including their legs.

The spiders had become extremely rare and had been listed as endangered in 2011.

But numbers are now booming thanks to conservation staff at Chessington World of Adventures.

Over a two-year period, staff reared and released four hundred fen raft spider-lings into the wild at Suffolk Wildlife Trust.

Fen raft spiderlings were released into the wild over the past two years to boost their population

The project has been so successful that the wild numbers of the spiders have almost doubled during this time and the zoo no longer needs to rear more to ensure their survival.

The spiderlings were released into the wild over the past two years to boost their population

Chessington World of Adventures has now been awarded for its work at the annual BIAZA awards, which awards zoos for conservation work across the country.

Keith Russell, a supervisor within the zoo team at Chessington, said: “The successful work on reintroducing the fen raft species is a great example of the good zoos can do in helping conserve endangered species in the wild.

“Here at Chessington we are very pleased to have received such high praise and recognition from BIAZA for the part we played in this project.”

[Related story: Britain's most poisonous spider revealed]

Picture credit: Chessington World of Adventures