The new study, published online in the journal Science Thursday, Feb. 28.
Flowering plants produce "male" and "female" varieties. Male plants produce pollen, and female grow flowers, which when pollinated, become fruit. Since plants can't move, insects or other animals are needed to carry pollen from the male plant to the female.
(Some plants use wind, but they have specialized pollen.)
Without insects to pollinate them, crops can't make food.