The endoparasitoid wasp, Meteorus pulchricornis (Wesmael), introduces virus-like particles [M. pulchricornis VLP (MpVLP)] and venom into its lepidopteran host larvae upon oviposition. These wasp-associated factors are considered to help impair some host functions including immune defense. To obtain the major protein repertoire of the MpVLP and venom that might support successful parasitism, we constructed a conventional cDNA library of the venom gland filament that produces both of them, and sequenced cDNA clones arbitrarily in the 5' regions. The 5' expressed sequence tags obtained from 473 independent cDNA clones were grouped into 228 clusters. One hundred and five of these clusters were annotated with one or more gene ontology (GO) terms by Blast2GO analyses. While the major repertoire of the M. pulchricornis venom gland shared some constituents with those of the venom glands of other parasitoid wasp species, it was distinct from those encoded by polydnaviruses. Twenty clusters selected for further analyses were fully sequenced and characterized again. Among them, 17 factors were subjected to quantitative reverse transcription polymerase chain reaction analyses, and 12 factors were suggested to be highly adult specific. Among these 17 factors, ten were tested as RNA interference targets, and effective gene silencing was observed for five factors. These five factors included two components of MpVLP. The MpVLP deficient in the two factors prepared from the knockdown wasps was less effective than the wild-type MpVLP in terms of the inhibitory activity against host hemocyte spreading estimated in vitro.