A tiny beetle that devours heather is advancing through Scotland, putting the grouse-shooting industry in jeopardy.

The warning is coming on the day of the Glorious Twelfth which marks the official start of the season.

The grubs eat heather, which is a staple of the grouse diet, and provides cover from natural predators.

Experts say the bug has struck in southern Scotland with a large outbreak on Langholm Moor.

Three mild winters in a row are thought to have encouraged the beetle's expansion.

Despite the threat, gamekeepers are recording a good year for grouse numbers.

They are up by almost 25% in total on 2008, with Angus, Moray and Nairn all reporting small increases.

However, parts of Dumfrieshire, Ayshire, and Lanarkshire have seen drops in population blamed on previous outbreaks of ticks and predators.

The shooting industry is worth £30million to the Scottish economy and supports around 600 jobs.