The insect get attracted by the smell of the flower and move towards it to suck nectar . Pollen grains are a sticky substance and when insect set on flower the pollen grains get stick to its legs and after when insect sets on any other flower the pollen grains get transferred to that female flower and reproduction takes place .
so in this way insect play a significant role in reproduction of plants.

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The pollen grains stick to the insects body as it goes to another flower cross pollination accors