If the pollen is to be transferred by insects it does not need to be so dry and powdery, or so abundant as in the other case, for the insect passes directly from one flower to another, without any random scattering of the pollen. Only winged insects are used for this purpose, as those which must creep, or rather walk, would brush the pollen from their bodies by rubbing against the various obstructions in the way. The insects most commonly used are the numerous kinds of bees, wasps, butterflies, and moths. These insects visit the flowers for different purposes. The butterflies and moths are after the nectar, while the bees and wasps feed upon the pollen. Visiting insects are therefore often grouped as nectar feeders, and pollen feeders, but in either case they are instrumental in transferring the pollen. The fourth or innermost part of the lily flower is an organ called the _pistil_. It stands in the center of the flower and is composed of three distinct regions. At the base it is bulbous and hollow, containing the bodies which are to become seeds. This bulbous region is called the _ovary_, and the little bodies it contains, which, through the action of the pollen, are to become seeds, are called _ovules_. Rising from the top of the ovary is a slender, stalk-like part called the _style_; and at the top of the style is a knob-like region called the _stigma_. The most essential region of the pistil is the ovary, for it contains the ovules. Next in importance is the stigma, for it must receive the pollen-grains. The style is of least importance, and therefore is sometimes wanting, the stigma being directly upon the ovary. The duty of the style, when it is present, seems to be to put the stigma into a favorable position to receive the pollen. It must not be supposed that the stigma always resembles a knob-like top to the style. It is really only a surface prepared to receive pollen, so it may be upon the top of the style, or may run like a line down one side of it, or may display itself in some other way. The pistil of the lily, however, is not a single structure. If the ovary be cut across, it will be found to be made up of three compartments, each one of which contains ovules. Each one of these compartments represents a unit of structure which has entered into the formation of the pistil. These units are called _carpels_, and the pistil of the lily is made up of three carpels. In this case the three are distinct only in the ovary, and have completely lost their identity in the region of the style. In many relatives of the lily, however, the three carpels are kept distinct in the style region, three styles or a three-parted style appearing upon the ovary.