Parental host species affects behavior and parasitism by the pentatomid egg parasitoid, Trissolcus japonicus (Hymenoptera: Scelionidae)

The samurai wasp, Trissolcus japonicus, is the primary natural enemy of the invasive brown marmorated stink bug, Halyomorpha halys, in its native range of Asia. Laboratory tests have found that the wasp can parasitize numerous native pentatomid species in North America, yet many potentially influential factors involved with T. japonicus host acceptance and host suitability are understudied. In this study we evaluated the effects of host related semiochemicals and parental host species on T. japonicus host foraging behavior and host parasitism. To address possible influences of parental host species, separate parasitoid lines were established using H. halys and native predatory pentatomid Podisus maculiventris eggs as hosts. Female T. japonicus from both host types were exposed to soybean (Glycine max) leaf surfaces contaminated by adult kairomones of either host species in behavioral assays. Females from each host type were also subject to no-choice tests in which they were exposed to either H. halys or P. maculiventris egg masses in large mesh cages. Each female used in the no-choice tests was weighed and their right hind tibiae were measured to identify possible phenotypic plasticity. Results from the behavioral assays suggest that T. japonicus exhibits some degree of host fidelity while searching for hosts. Females which emerged from P. maculiventris eggs resided for equal amounts of time on leaves contaminated with kairomones from either stink bug species. Differences in no-choice test performance were not found between the two host types, as parasitism rates and host suitability were determined to be dependent on exposed host species and not the parasitoid parental host species. T. japonicus which emerged from H. halys possessed longer right hind tibiae and weighed roughly twice as much as wasps which emerged from P. maculiventris.