Development ofTrichogramma australicum (Hym.: Trichogrammatidae) at low and high population density in artificial diet

Abstract

We compared the development of Trichogramma australicum Girault in artificial-diet filled artificial "eggs" containing 10-15 (low density) or 35-50 (high density) immature parasitoids. The size of low- and high-density T. australicum eggs at 1, 15, 30 and 36 h was not significantly different. Also, incubation time of low- and high-density eggs in artificial diet was similar. Appearance of urate bodies in larvae developing low and high density occurred at the same time (100-108 h). Size of immature T. australicum in low density significantly increased after the urate bodies had appeared. Black deposits appeared on the surface of T. australicum prepupae soon after all diet had been consumed (at 108-120 and 144-168 h in low and high density, respectively). We concluded that the appearance of the black deposits was an indication of the onset of the prepupal stage. The pupal size was significantly larger at low density than high density. Mortality of prepupae and pupae was significantly higher at low density than at high density. Proportion of larvae at high density developed to abnormal and normal wasps. Wasps did not emerge from larvae reared at low density.