During plant reproduction, pollen grains need to move from the anther of one flower to the stigma of another flower. This is called pollination. Insects can pollinate flowers, and so can the wind. Insect-pollinated flowers are different in structure from wind-pollinated flowers. This table describes some differences:

Insect pollinated plants and wind pollinated plants.  Insect pollinated plants are large and brightly coloured to attract insects.  They are usually scented and have nectar.  The number of pollen grains is moderate as insects transfer them efficiently.  The pollen grains are sticky or spiky so that they also stick to the insects.  The anthers are inside the flower, stiff and firmly attached to brush against insects.  The stigma are inside the flower and are sticky to that pollen grains stick to them when an insect brushes past.  Wind pollinated flowers are small and often dull green or brown as no need to attract insects.  They have no scent or nectar.  There are large amounts of pollen grain as most are not transferred to another flower.  The pollen grains are smooth and light, so are easily carried by the wind without clumping together.  The anthers are outside the flower, loose on long filaments to release pollen grains easily.  The stigma are outisde the flower and are feathery. They form a network to catch drifting pollen grains.

We depend upon pollination by insects (including the honey bee) for many of our crops. Without them the security of our food would be threatened.