Frozen pupae of Chrysomya megacephala (Diptera: 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 Nasonia vitripennis (Walker) was evaluated. Several treatments were simultaneously exposed to female parasitoids on a free-choice basis, and separate lots were also exposed to infestation in parallel. A ratio of one female parasite/host pupa was used. Lots of viable pupae of C. megacephala not submitted to N. vitripennis were used as controls. The reproductive activity of parasitoids was monitored for 24 hours. Previously frozen pupae gave origin to as much as 50% the number of adult parasites obtained from fresh pupae. The free choice feature permitted the possible occurrence of hyperparasitoidism in host pupae not submitted to freezing, with a consequent reduction in the final number of parasite offspring obtained in this treatment. On the other hand, frozen pupae presented significant success rates as a breeding substrate for N. vitripennis (more than 80% on average). The freezing and thawing process adopted did not influence the time of preimaginal development of the parasite. However, a marked increase in female sex ratio was observed in the treatments submitted to freezing.