Total dependence: Yuccas and Moths
Sometimes plant and insect become totally independent on each other. Yucca plants which produce rosettes of cream flowers attract a small moth with a specially curved proboscis that enables it to gather pollen from the yucca stamens. It moulds the pollen into a ball and the carries it off to another yucca flower. First it goes to the bottom of the flower, pierces the base of the ovary with its ovipositor and lays several eggs on some of the ovules that lie within. Then it climbs back up to the stigma rising from the ovary and rams the pollen ball into the top. The plant has now been fertilized and in due course, ovules in the base of the chamber develop into seeds. Those that carry the moth's eggs will grow particularly large and be eaten by the developing caterpillars. Those ovaries without caterpillars will not be eaten and permit the yucca to propagate itself.