Reproduction by cross-pollination of many plant species depends on bees. They thus help preserve biodiversity and contribute to the yield of crops, three-quarters of which are dependent on pollinating insects. They also allow the survival of many animals, birds, and insects species. By foraging on nectar flowers, bees load their legs with the pollen produced by the stamens of the flower. They then transport it in the form of balls and deposit it on the pistils of other flowers.