In a British poppy field, David Attenborough talks about how co-operative plants bribe insects to pollinate them, supplying pollen and nectar for them to eat in return for their acting as couriers. Bumblebees have a great taste for pollen, gathering it with special combs on their legs and packing it into baskets on their thighs. As they move from flower to flower, some of the pollen that gathers on their hairy bodies brushes off on another flower and the plant's purpose is accomplished. Pollen, packed with genetic matieral, is a complex and expensive commodity and many flowers offer a much cheaper bribe of nothing more than sweetened water, or nectar. Produced in nectaries in the heart of the flower, insects such as honey bees have to brush past the pollen to reach it. In temperate lands, flowers are only produced in spring and summer when there's no frost. So insects that shelter from the winter in nests have to stock up while they can.