Technical Abstract: The pear psylla, Cacopsylla pyricola, and related psyllids are important pests of pear worldwide. To improve our understanding of the impact made by the various predators of pear psylla we developed antibodies against this pest to be used in detecting prey remains in the predator¿s guts. Antibodies were developed in mice by immunization with homogenates from various life stages of the pear psylla and subsequent hybridoma production. Over 900 antibody-producing cell lines were screened for activity against pear psylla antigens and ultimately four of these were found to be useful. Two monoclonal lines produced antibodies that showed selective activity against all stages of psylla except young eggs. Two other monoclonal lines showed activity only to psylla eggs. Both types showed significant cross reactivity to other Psyllidae species. Pear psylla remains were sensitively detected in the predatory bugs Anthocoris tomentosus Péricart (Heteroptera; Anthocoridae) and Deraeocoris brevis (Uhler) (Heteroptera: Miridae) in laboratory feeding trials and in field studies using the monoclonal which detects nymph and adult stages. The utility of these antibodies for the study of trophic interactions and habitat management in relation to biological control of pear psylla is discussed.