A hunt across Britain is being launched for a “fab four” quartet of oil beetles, which are at risk of vanishing from the countryside.

The number of oil beetle species found in the UK has halved in the past 100 years and the remaining four, which are often found around the coasts and particularly in the southwest, are under threat.

They have been hit by the loss of flower-rich habitats and reductions in wild bees, which they use as unwitting hosts for their young.

Now Buglife and the National Trust are launching a survey with government conservation agency Natural England and Oxford University Museum of History to help establish the whereabouts of the four remaining species of oil beetle.

They are asking the public to report sightings of oil beetles, which are normally found between late March and June and can be spotted on wildflower-rich grasslands, heathlands, moors and coastal areas, such as cliff tops.

They are easy to spot on bare ground at the edge of footpaths, where females like to dig their burrows.

Oil beetles have an unusual life-cycle, in which they lay up to 1,000 eggs in a burrow in soft or sandy soil, which hatch as long-legged, three-clawed larvae.

The larvae lie in wait on flowers to hitch a ride on mining bees and are taken back to the bee’s nests, where they change into a maggot-like creature which devours the bee’s egg and pollen stores, before emerging as an adult the following spring. The adult beetles are flightless, large and slow-moving, and get their name from toxic oily secretions produced as a defence against predators.

TV presenter and Buglife vice president Nick Baker said: “They’re big, bold beetles with a lustre that would put any oil droplet to shame.

“They are also unique in their highly complex life cycle and when you get to know them, it makes you realise what a miracle each and every beetle is.”

The four species found in the UK are the black oil beetle (Meloe proscarabaeus), the violet oil beetle (Meloe violaceus), the rugged oil beetle (Meloe rugosus) and the short-necked oil beetle (Meloe brevicollis).