A RARE beetle thought until recently to have died out in Britain has been found living in numbers on a Scottish island.
• Mystery surrounds how the short-necked oil beetle, which cannot fly, has landed up on Coll. Picture: Complimentary
The discovery of a population of short-necked oil beetles has excited entomologists as the insects had not been seen for about 60 years until rediscovered in Devon in 2007.
But an expert on holiday on the island of Coll reported seeing the oil beetle last month and a team travelled to investigate the discovery and to look for other species.
Now the team is trying to establish how the insects, which cannot fly, got to the island.
Surprisingly, the team did not find any oil beetles on neighbouring Tiree, despite it having similar conditions.
About 40 beetles were found on four sites on Coll, examined by the team, which includes Jeanne Robinson, the curator of entomology at Glasgow Museums; Geoff Hancock, of Glasgow's Hunterian Museum; Garth Foster, of the Aquatic Coleoptera Trust, and beetle expert Darren Mann of Oxford University Museum of Natural History. It is thought that the beetle population might be much larger.
Until the small colony was found in Devon, it was thought the insect, Meloe brevicollis, had been extinct in the UK since the 1940s due to intensive farming.
Ms Robinson said: "It's hard to believe it could have been present in those numbers for some time. Almost definitely, there is a bigger population than what we have found so far.
"We were there for only two and a half days and there is a certain amount of chance and luck involved (in finding the insects].
"They are very vulnerable to disturbance and what the Devon and Coll sites have in common is that they have been relatively undisturbed for a long time."
The beetle has parasitic young that depend on solitary nesting bees for survival. Ms Robinson added: "The beetle does not fly and relies on the bee carrying its young to disperse it, so how it got to Coll remains quite interesting.
"We are hoping there is the potential to do some genetic analysis so see where the population came from."
She said there were records of the beetle being found in Ireland and it was feasible that bees had flown over the island bearing the oil beetle.
She added: "We went first to Tiree, which also has huge population of the solitary bee that the oil beetle relies upon and nice sand dunes as well, but we just did not find anything. Coll is a bit more rugged and there are subtle difference in conditions."
Ms Robinson said that the solitary bee population on Coll was doing "incredibly well' because of the quality of its sand dunes, which are very sheltered and remain largely undisturbed.
She said there was a delicate balance between the beetles and bees as the former - whose larvae feed on the bees' young and pollen stores - would not survive if it decimated the bee population.
The entomologists' discoveries will be listed on the National Recording Scheme and Natural Biodiversity Network which allows changes in populations and biodiversity to be monitored.
The oil beetle gets its name from the highly toxic oil secretions it produces when threatened. The discovery in Devon was made by an amateur entomologist during a wildlife survey on National Trust land.
Prior to that, the beetles were last recorded at Chailey Common, Sussex in 1948.