[Use of parasitic wasps (Hymenoptera: Pteromalidae) in the biological control of domestic flies in pig housing].

Adaptability of two parasitoid species S. nigroaenea and M. zaraptor to conditions of stable microclimate was investigated in a farrowing house. The colony was reared in an insectary at a temperature of 24-26 degrees C and relative humidity of 60-70% in cages of the size 0.3 x 0.3 x 0.2 m. The development of the species M. zaraptor from egg to adult lasted 19 to 23 days, in S. nigroaenea it was 23 to 25 days. Rates of parasitism of house fly pupae were followed in plastic pots (8 x 4 x 9 cm) with larval medium for fly rearing. The larval medium consisted of milk powder, wheat bran and dried yeast. Both species were demonstrated to be able to penetrate to pupae in deeper layers of the medium (Tab. 1) and in this way to control the amounts of fly adults after their eclosion. The results were evaluated by Student's t-test. 98% of flies in the stable were house flies (Musca domestica L.), the remaining flies were stable flies (Stomoxys calcitrans L.). No parasitoids were observed in the stable. Two pots containing 2-3,000 pupae parasitized by S. nigroaenea and M. zaraptor were placed in the stable on 30th January 1990. Parasitoids were monitored at three locations of the stable according to parasitism rates of lab-reared house fly pupae exposed in plastic pots with larval medium. Twenty-two checks were made in 2 to 4 week intervals from February to November 1990, and one final check after a six-month interruption (Tab. II). Both species persisted in the stable for the whole period of observation (Fig. 1). The species S. nigroaenea, the population levels of which were much higher, showed the greater migration activity after its individuals had been released to the stable. Sprayings with the Alfacron insecticide were performed in the stable in March and September 1990 in the course of this experiment.