THE COMPARATIVE BIOLOGY OF THE PUPAL ENDOPARASITOID PSYCHOPHAGUS-OMNIVORUS (HYM. PTEROMALIDAE) ON 3 CANDIDATE LEPIDOPTERAN HOSTS

Laboratory trials designed to investigate the biology of the gregariou s endoparatsitoid Psychophagus omnivorus (Hym.: Pteromolidae) on pupae of the pest species Chrysodeixis chalcites, Spodoptera exigua or Laca nobia oleracea (Lep.: Noctuidae) reveal that each of these candidate h osts can be used as oviposition sites. In all cases, wasp fecundity is high and generation is rapid. A minimum of 10 daughters is produced b y each P. omnivorus female every 3.5 weeks. Patterns of host attack an d the distribution of wasp brood size vary according to the identity o f the available host. Chrysodeixis chalcites and L. oleracea pupae are attacked at a moderate rate, but individual hosts support large brood s. By contrast, individual S. exigua hosts sustain smaller broods, but these hosts are parasitised at a higher rate. When P. omnivorus encou nters C. chalcites or L. oleracea, most host-attacks occur within the first 10 days of her adult lifespan. However, when P. omnivorus is pre sented with S. exigua the oviposition period is prolonged until the fi fth week of host-exposure. These differences between the oviposition s trategies adopted by P. omnivorus against each host type have implicat ions for its use as a biocontrol agent.