I discovered this beautiful bug at an altitude of about 1540m in a karst limestone region of the Western Rodopi Mountains in Bulgaria in August 2006. Despite its striking colour (scarlet red with pale yellow markings and rim), I have still not been able to identify it and would be grateful if anyone can suggest an ID for it.
Although I have never personally seen an example so highly coloured ,I think this is a shield bug ( jalla dumosa ) that is certainly found in the region.If you google there are a couple of pictures similar to yours.
I have been away in the mountains doing research during May and haven't had the chance to thank you both for giving me an ID for the shield bug! The amazing red colour really threw me. It seems an oddly conspicuous coluration for a shield bug!