The capability of aquatic plant managers to successfully control aquatic plant infestations is highly dependent on their ability to access pertinent and up-to-date information on scores of topics within the broad areas of ecology, biology, and environmentally compatible management techniques. Such a task is becoming increasingly difficult because the existing knowledge base-in the form of technical reports, journal articles, oral presentations, videotapes, etc.--is already sizable and is increasing rapidly. An efficient mechanism is needed to access such diverse and important information. Toward this goal, researchers at the U.S. Army Engineer Waterways Experiment Station have developed a computer-based information system known as APIS (the Aquatic Plant Information System). The APIS program is the result of combining several information systems into one integrated package. Among the components are systems to identify insect herbivores of aquatic plants, an aquatic plant identification system, and research-grade information systems to identify male leaf-mining flies in the genus Hydrellia and to determine the physiological age of female Neochetina elchhomiae.