FROZEN PUPAE OF CHRYSOMYA-MEGACEPHALA (DI PTERA, CALLIPHORIDAE) - PRELIMINARY-STUDY AS BREEDING SUBSTRATE FOR NASONIA-VITRIPENNIS (WALKER) (HYMENOPTERA, PTEROMALIDAE)

The use of Chrysomya megacephala (fabricius) pupae, submitted to cold storage (-12 degrees C) for 1 to 4 months as breeding substrate for Na sonia vitripennis (Walker) was evaluated. Several treatments were simu ltaneously exposed to female parasitoids on a free-choice basis, and s eparate lots were also exposed to infestation in parallel. A ratio of one female parasite/host pupa was used. Lots of viable pupae of C. meg acephala not submitted to N. vitripennis were used as controls. The re productive activity of parasitoids was monitored for 24 hours. Previou sly frozen pupae gave origin to as much as 50% the number of adult par asites obtained from fresh pupae. The free choice feature permitted th e possible occurrence of hyperparasitoidism in host pupae not submitte d to freezing, with a consequent reduction in the final number of para site offspring obtained in this treatment. On the other hand, frozen p upae presented significant success rates as a breeding substrate for N . vitripennis (more than 80% on average). The freezing and thawing pro cess adopted did not influence the time of preimaginal development of the parasite. However, a marked increase in female sex ratio was obser ved in the treatments submitted to freezing.