To reproduce sexually, any organism has the problem of bringing the male cells from one individual to the female cell of another of that species. Lacking the ability to move from place to place, plants rely on other things to do the transferring of male cells to female cells for them. The process is called pollination because the male cells are in the pollen. One way they do this is by using the feeding of insects . In fact, the insect can usually see a much brighter flower than you can, since it can see in the ultra-violet.
White flowers are good reflecters of UV light, so they are very prominant to an insect's eyes.
When it arrives at the flower, the insect may go straight for the sweet, sugary nectar hidden deep in the flower, or it may actively collect pollen like this bee does. Look at the pollen sacs on its legs. Being messy feeders, the insects get covered in pollen grains from ripe anthers. To get at the nectar, the insect has to push past all the other internal parts, so it will pick up pollen from a flower whose anthers are ripe. When it visits another flower, the pollen grains from its body may rub off onto a ripe stigma .