If we can get it right for these beetles, the knowledge gained will help a lot of other species on the action plan

Dr Roger Key, English Nature

The creature, Cryptocephalus coryli, was once quite common across England but is now, like other pot species, in sharp decline and restricted to just a handful of breeding locations.

Conservationists released more than 200 larvae at a site at Whisby in Lincolnshire. The grubs have been tagged with slivers of stainless steel to allow their progress among the plants and debris on the ground to be monitored with a metal detector.

Researchers want to learn more about the beetle's behaviour so that a strategy can be developed to preserve the animal in its natural habitat.

Food sources

Hazel pot beetles have their unusual name because the female adult lays her eggs in containers she constructs from her own dung.

The beetle, which lives on young birch trees, then throws the pots down on to the ground. She also cuts leaves from the bush which fall around the encased eggs.

Researchers are not certain but they think these leaves may provide an early food source for the larvae when they hatch. The grubs drag their protective pots around with them as they forage in the undergrowth.

As they grow, the larvae must also use their own waste to extend the size of their pots. In the end, the pot has the shape and size of a rat dropping.

Action plan

"What we do know is that the adults are sun lovers," said Dr Steven Compton from Leeds University.

"They're after small bushes with a small screen of trees on a south-facing site. But this is only ever a temporary home because trees grow and produce shade, so the beetles have to move on every few years."

Dr Compton said it was possible that fragmentation of the landscape had made it difficult for Cryptocephalus coryli to disperse and find new breeding sites.

Whatever the cause of its decline, the hazel pot beetle is now one of 83 rare beetles listed in the UK's Biodiversity Action Plan, which was established to find ways of securing the future of the nation's most endangered species.

"The aim is to find out where these larvae go - where they over-winter," said Dr Roger Key, a senior invertebrate specialist from English Nature, which is working on the project with Leeds University and the Lincolnshire Wildlife Trust.

"This will tell us about their conservation ecology. And if we can get it right for these beetles, the knowledge gained will help a lot of other species on the action plan."