Leafminers are usually the larvae of flies, moths, or beetles that feed or "mine" between the upper and lower epidermal leaf surfaces. The larvae tunnel through the leaf creating a narrow, whitish colored serpentine (winding) mine or blotch (blister) type mine. The tunnel is clear, except for the trail of black fecal material left behind as larvae feed. Female flies puncture or "stipple" leaves with their ovipositors to lay eggs in the leaf tissue or to feed on sap. Many ornamental plants are attacked by leafminers, but azalea, bougainvillaea, ixora, hollies, chrysanthemum, lantana, oak, and boxwood are some of the preferred hosts. Leafminer damage is very obvious, but healthy plants should be able to tolerate considerable injury before losing vigor or yield. However, during heavy infestations, plants appear bleached or faded and their aesthetic value is reduced. In some cases, the leaves turn yellow and drop, due in part to the entry of pathogenic fungi and bacteria into old mines. The following are examples of some common leafminer species, but many more species exist.