Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) is a naturally occurring ectoparasitoid of wood-boring longhorned beetles (Coleoptera: Cerambycidae). To determine mechanisms involved in this host–parasitoid relationship, we extracted and partitioned the proteomes from neonate and the late-stage D. helophoroides larvae using iTRAQ-based HPLC-MS/MS analysis, followed by functional enrichment and protein–protein interaction analyses. In all, 50 putative venom proteins were identified from the proteome of D. helophoroides larvae. Of those, 19 were identified as arginine kinases, 10 were chitinases, and 21 were either proteases or protease inhibitors. These results serve as a major advance in understanding the parasitism mechanism of this ectoparasitoid, as well as the potential for developing environmentally safe chemistries based upon these venom proteins that might be used in cerambycid control in forest management.