none The soluble organic fraction of diesel particulate emissions was tested for physiological and genotoxic effects on the parasitoid wasp, Bracon hebetor. Adult female survival after topical treatment was significantly decreased at the higher concentrations of SOF. Daily egg production, a sensitive assay for genotoxic and physiological effects, was not significantly affected at any concentration. Egg hatchability on Days 1-5, representing vitellogenic oocytes at the time of treatment, was decreased, but this effect lacked consistency and dose dependence. An extensive dominant lethal test was performed with negative results. Possible explanations for these findings and comparisons with in vitro tests such as the Ames test and sister chromatid exchange are discussed.