In the effort to manage the hemlock woolly adelgid in eastern North America, two fly species deployed as biological control agents are themselves targeted by parasitoid wasps. A new study examines how these parasitoids affect the flies and other predators of the hemlock pests. Shown here is a hemlock branch infested with hemlock woolly adelgid (Adelges tsugae), left; an adult female Leucotaraxis argenticollis fly, center, whose larvae feed on the adelgid; and a wasp in the genus Pachyneuron that parasitzes L. argenticollis larvae or pupae. (Fly photo courtesy of Cornell University Insect Collection and New York State Hemlock Initiative [NYSHI]. Hemlock and wasp photos courtesy of NYSHI.)