Why do Bees Die?

Honey bees do not only supply us with a sweet spread for our breakfast rolls, they are regarded as the third most important pet: their main task is the pollenisation of fruit, vegetables and wild plants. A third of all human food is directly or indirectly dependent on them. In parts of the USA over 70 per cent of all bee colonies have completely disappeared since last autumn. There is still speculation as to the cause of this mysterious mass fatality. What happens when there are no more bees?