Studies On The Parasitic Characteristics Of Pachycrepoideus Vindemmiae (Rondani) On Two Fly Pupae

The parasitic characteristics of Pachycrepoideus vindemmiae (Rondani) (Hymenoptera: Pteromalidae) parasitized on Bactrocera dorsalis (Hendel) and Musca domestica Linnaeus were observed in the laboratory. The result showed that the developmental periods of this pteromalid parasitized on B. dorsalis were 1 day for eggs, 9 days for larvae, 1 day for prepupae and 8 days for pupae at 25±1℃. The female pteromalid adults could oviposit on hosts as soon as emergence. The parasitism rate on B. dorsalis was decreased with the increase of the adult age, and the parasitism rate was the highest within 1 to 2 days after female adults emerged. The pupae of B. dorsalis from the first day to the ninth day after pupation could be parasited by P. vindemmiae, however, the parasitism rate on the third day pupae was the highest. The parasitism rate fell while the age of pupae increased. There was a good correlation between the host density and its parasitism. It could be described with Holling model: N_a=2.5182T_tN_o/(1+2.5182T_hN_o). The interfere effect by the density of pteromalids could be described with Hassell-Varley model: a=0.0520P^-0.2368. The linear correlation between the effective accumulated temperature and development speed could be indicated by the formula T=6.4712+344.75V. The pupae of M. domestica from the first day to the fourth day after pupation could also be parasitized by P. vindemmiae, whereas the parasitism rate on the second day pupae was highest. The parasitism rate also fell while the age of pupae increased. The parasitism rate and emergence rate of the pteromalids parasitized on M. domestica were serious affected by their density. The parasitism rate raised when the density of pteromalids increased. The papae of B. dorsalis in the sand at 1 cm depth could not be parasitized by P. vindemmiae, but the pupae of M. domestica at the same place could be parasitized. Neither of fly pupae in the sand at 2-4 cm depth could be parasitized. P. vindemmiae preferred the pupae of Musca domestica as hosts to that of B. dorsalis.