An Italian honeybee pollinating an avocado blossom

Avocados have an odd system of pollination to insure cross pollination. Each of the inconspicuous green/yellow flowers has both male and female parts, but only one sex is open at a time to prevent self fertilization. There are two kinds of trees, A and B types. The A type trees have their flowers open in the mornings as females. The flowers close by afternoon, and remain closed until the following afternoon, when they reopen with the male parts now producing pollen. The B type trees open their flowers as female in the first afternoon, they close and reopen as males the following morning. Each flower only opens twice. If a grove is properly planted with both types of trees, and if pollinators are present then a good set of fruit is likely. Honeybees do the vast majority of the pollination here, but wild bees, flies, wasps and even hummingbirds are also seen working the flowers.