A tagged queen bee is pictured on a honeycomb in Vienna July 11, 2012. A growing number of urban beekeepers' associations, such as Vienna's Stadtimker, are trying to encourage bees to make their homes in cities, as pesticides and crop monocultures make the countryside increasingly hostile. Bee populations are in sharp decline around the world, under attack from a poorly understood phenomonenon known as colony collapse disorder, whose main causes are believed to include a virus spread by mites that feed on haemolymph - bees' "blood". Picture taken July 11, 2012. REUTERS/Lisi Niesner (AUSTRIA - Tags: ENVIRONMENT ANIMALS TPX IMAGES OF THE DAY) Published: Čec. 25, 2012, 2:07 odp.