Parasitisation activity of Spalangia cameroni and Muscidifurax zaraptor, pupal parasitoids of Musca domestica

The house fly, Musca domestica L. (Diptera: Muscidae), is a significant pest in livestock farms and a major concern for both humans and farmed animals due to its ability to transmit over 200 pathogens. The use of pupal parasitoids is a sustainable strategy for controlling this pest. Spalangia cameroni Perkins (Hymenoptera: Spalangiidae) and Muscidifurax zaraptor Girault & Sanders (Hymenoptera: Pteromalidae) are commonly used as biocontrol agents for M. domestica. The objective of this study was to determine the oviposition peak of female parasitoids in relation to their age and the sex ratio of the adult progeny. For both species, 20 fresh M. domestica pupae (24-48 h old) were provided daily to each fertilised female for 14 days, after which the pupae were checked for parasitoid emergence. A control group of 20 pupae without female parasitoids was maintained. The results showed that S. cameroni had a higher overall percentage of parasitisation (57.7%) compared with M. zaraptor (32.4%). The parasitisation ratio of S. cameroni remained almost constant throughout the 14-day period, whereas that of M. zaraptor decreased drastically after Day 11. Peak oviposition for S. cameroni was on Day 5 with 13 parasitised pupae per female, whereas M. zaraptor parasitised eight pupae per day on 4 days during its peak oviposition period (between Days 3 and 8). The newly emerged parasitoids had a skewed sex ratio towards females: 81% for S. cameroni and 66% for M. zaraptor. The presence of these parasitoid species resulted in fewer new house fly emergences than in the control group, where natural pupal mortality was lower in the absence of parasitoids. These findings may be useful for optimising the mass production and time-use of the two parasitoid species for the management of house flies in livestock farms.