none Bleomycin (BM) induced dominant-lethal genetic lesions in the gametes of both sexes of adult Bracon hebetor wasps following ingestion. This effect was demonstrated by decreased fertility in the unfertilized eggs of treated females as well as in eggs fertilized by mature sperm derived from treated males. Death in the unhatched eggs occurred prior to blastoderm formation indicating BM caused chromosome breakage. Affected ovarian cells were limited to those exposed to BM between the developmental stages of vitellogenesis and early metaphase I. Sperm-associated fertility reductions were temporary in duration with substantial reductions being observed starting on the second day following the initiation of oviposition. BM lowered general egg-formation capacity in treated females but, unlike the fertility effects, decreased fecundity was caused by somatic debility. Although the BM-induced genetic damage observed in B. hebetor was radiomimetic in nature, the time of appearance and duration of the effects did not correspond with previous patterns found when B. hebetor adults were exposed to X-rays. While the differences could be due to the BM detoxification or the repair of BM-induced chromosome damage, further investigation would be required to demonstrate the presence of such systems in this hymemopteran.