Many plants have extrafloral nectaries that produce nectar even during periods in which the plant is not flowering. A. Evolutionary history shows that plants that produce extrafloral nectar originated in the tropics. B. Extrafloral nectar has a higher concentration of sugar than floral nectar and is more attractive to ants and other insects. C. The protectionist hypothesis is that extrafloral nextar attracts ants, and that the ants, in order to preserve this energy-rich food source, attack insects that might harm the plant. D. Evidence accumulated during the twentieth century proved that ants provide significant benefits for plants with extrafloral nectaries. E. Research has shown that American morning glory plants that are protected by ants produce significantly more seeds than morning glory plants that are not protected by ants. F. Ants generally ignore small insects, but they will eat the adults of large insect species as well as their eggs and larvae.