The Fen Raft spider is one of the country's most endangered species of spider. With an adult leg span of 4 inches across they are also the largest native spider to the UK.
They are only found in three locations in the UK, with declines in their wetland habitat and water quality causing their numbers to plummet.
Now Chessington World of Adventure is leading a project to hand-rear 200 baby fen raft spiders for release into the wild.
The spiderlings will be raised in test tubes and hand-fed fruit flies every four days before being released into the wild in October.
Bob Ward, reptile keeper at Chessington Zoo, said: “Having to feed 200 spiders one at a time is certainly a challenge, but it’s vital to help see them through the most vulnerable period of their lives before they are released back into the wild, as they will then have a much better chance of surviving."
Raft spiders are one of just two British spiders protected under law because they are so endangered. They are now found in just three places in East Sussex, Swansea and the Suffolk/Norfolk border.
Their large hairy legs allow them to float on the water of the fens and wetlands, where they hunt sticklebacks and tadpoles underwater.
Currently the tiny spiderlings measure just a few millimetres across but they will grow to be up to four inches in size as adults.
Mr Ward added: "The spiders’ mums were collected from the wild in June when they carry their eggs in huge silk sacs held in their mouths.
"When the babies emerge from the sac the mother guards them in a big silk tent called a nursery web. In the wild the babies leave the web after about a week to fed for themselves. Our captive mums made their nurseries in five-litre water bottles.