Bees and many plant species are mutually dependent, the plants needing bees for their pollination, the bees needing plants because it is from the flowers that they collect all their food. This relationship stems from Cretaceous times, roughly 100 million years ago, when the angiosperms (flowering plants) started to evolve. To transfer their pollen from one individual flower or plant to another of the same species, they began using pollinators instead of depending on wind and water as did their evolutionary ancestors. In order to attract pollinators angiosperms offer rewards in the form of pollen, nectar or oil, and make themselves conspicuous by developing flowers. Several insect groups evolved because they exploited these food sources, but none of them exploited them to such an extent as bees. Unlike butterflies and moths, flies or beetles, who only consume nectar and/or pollen in their adult stage, adult bees also collect these substances to feed their larvae.