The crickets like to sunbathe in the sun and warm up before they feed
A rare insect has been released at two nature reserves in Surrey and Sussex in a bid to boost the population.
The field cricket nearly disappeared from the UK because of a decline in the heathland habitats it needs to survive.
RSPB ecologist Dr Jane Sears said the population was down to one colony at one point, but was now back up to five.
The flightless Gryllus campestris was released at the charity's reserves at Farnham Heath and Pulborough Brooks on Thursday.
The two sites are recreated heathlands, converted from commercial conifer plantations.
Conservationists collected crickets from other sites in West Sussex to try to develop colonies in the two locations.
Dr Sears said: "We nearly lost it in the UK because it needs short heathland and chalk grassland, with patches of bare ground.
"These habitats have been destroyed and fragmented over the years.
"It was down to a single colony at one point but it is now back up to five, and if these reintroductions are a success, we can add two more and help return them to our countryside."
According to the RSPB, the Gryllus campestris is the rarest cricket species in Britain.
Because the species is flightless, the crickets are unable to migrate long distances between the now-fragmented areas of heathland habitat.
One of their habits is to warm up before feeding. The insects make a sun-lounger in short grass so they can sunbathe.