While all of these answers are mostly true, you have to go back in time. Darwin called it the abomniable mystery. Flowering plants and insects co-evolved rapidly roughly 150 MYA. So prior to flowering plants, there were few plants and insects and they were mostly generalists. The rapid expansion and explosion of insect diversity is deeply entangled with the explosion of diversity in angiosperms.
the oldest pollinators, prior to bees,butterflies and other insects. were beetles, as evidence of magnolias one of the oldest lineage of flowers, use only beetles.
While all of these answers are mostly true, you have to go back in time. Darwin called it the abomniable mystery. Flowering plants and insects co-evolved rapidly roughly 150 MYA. So prior to flowering plants, there were few plants and insects and they were mostly generalists. The rapid expansion and explosion of insect diversity is deeply entangled with the explosion of diversity in angiosperms.
the oldest pollinators, prior to bees,butterflies and other insects. were beetles, as evidence of magnolias one of the oldest lineage of flowers, use only beetles.