A beetle the size of a bird was shot out of sky by a gun-toting Victorian insect collector, museum experts have discovered.

The Goliath beetle, from Africa, is housed at London's Natural History Museum.

Staff at the museum became became puzzled by small circular holes in the giant bug's tough carapace. But it was only when cameras started rolling for a BBC documentary on the museum that the mystery was solved.

Forensic scientist Heather Bonney confirmed that the beetle had been shot. Her investigation identified entry and exit wounds, and X-rays revealed a shotgun pellet still inside the the body.

The positioning of the wounds showed the beetle was in flight when it was bagged, but the pellets hit the creature's back and not its underside.

Experts think it must have been performing one of the high aerobatic displays that make Goliath beetles notoriously difficult to catch.

Beetle curator Max Barclay said: "Our collections are full of mysteries and every year scientists are discovering more about them and using them as evidence to help understand the world around us.

"The number of new discoveries just waiting to be made in these collections is astronomical, and every one of the museum's 70 million specimens has a story to tell."

Goliath beetles belong to the scarab family and are one of the largest insects on Earth, growing up to 4.5 inches long and weighing as much as 3.5 ounces. The Natural History Museum specimen is 3.9 inches long and described as being about the size of "a large sparrow or small blackbird".

The first episode of the six part documentary Museum of Life will be shown on BBC2 on Thursday, March 18.