Hydrilla verticillata is among the worst weeds in streams, rivers, and lakes in the southern US. This species forms dense stands, crowds out native vegetation, impedes navigation, and makes water management problematic. Hydrilla is controlled mainly with chemical herbicides; however both mechanical removal and biological agents (e.g. fish and insects) play some role. Since the discovery of herbicide resistance in hydrilla populations in Florida alternative forms of control, especially biological control, have become a high priority. Surveys for insects that feed on hydrilla in China discovered a beetle, Macroplea japana feeding underwater on the roots and stems. Subsequent studies determined that this insect completes one generation each year and occurs in the provinces Hubei, Hunan, and Guizhou. These beetles were found feeding as larvae on numerous aquatic plant species including Vallisneria spiralis, Potamogeton malaianus, Potamogeton maackianus, Potamogeton perfoliatus, Ottelia acuminata, Myriophyllum verticillatum, Nymphoides peltatum, and Alopecurus aequalis. Considering this wide range of plants, it is unlikely that M. japana will be used as a biological control agent for hydrilla.