The fly Leucotaraxis argenticollis (adult female shown at left) has been deployed as a biological control agent for the hemlock woolly adelgid (not pictured). However, a parasitoid wasp in the genus Pachyneuron (right) lays its eggs in either the larvae or pupae of L. argenticollis flies. Note: Images not to relative scale; scale bar for left image only. (Fly photo courtesy of Cornell University Insect Collection and New York State Hemlock Initiative [NYSHI]. Wasp photo courtesy of NYSHI.)