Improvement of survival of the house fly (Musca domestica L.) larvae under mass-rearing conditions.

Two new approaches were examined, aimed at increasing survival of the house fly (Musca domestica L.) larvae under mass-rearing conditions of a biodegradation facility: modification of the larval substrate and dispersal of the eggs during inoculation. The two types of pig manure used in this study (manure with sawdust and manure without sawdust) differed in terms of larval survival and nutritional value for the house fly larvae. Larval survival in manure without sawdust in the control treatment was low (46.8 ± 2.1%) and its nutritional value for the larvae were high. Addition of 5.7% of previously biodegraded manure did not significantly affect larval survival (52.3 ± 1.9%), but larval development was faster and the pupae were significantly smaller (14.28 ± 0.4 mg) compared to the control (16.29 ± 0.5 mg). Using alternative substrate for incubation of eggs and first-instar larvae significantly increased larval survival (63.3 ± 3.3%) and decreased the mean weight of produced pupae (14.39 ± 0.71 mg). Overall, the weight of recovered biomass in the alternative substrate treatment increased by 14.3 kg ton-1 of manure compared to the control. Larval survival in manure with sawdust was generally higher than 70%, but its nutritional value for the larvae was lower than in manure without sawdust. Dispersal of eggs over the surface of manure with sawdust significantly affected larval survival and mean weight of pupae. Larval survival was significantly lower (59.2 ± 4.0%) and pupae were significantly heavier (18.45 ± 0.8 mg) when eggs were applied to a small area on the manure surface (spot treatment), as compared to diagonal, Z-line and multiple zig-zag dispersal (72.5 ± 2.4 to 74.6 ± 3.0% and 14.76 ± 0.6 to 15.97 ± 0.6 mg, respectively). No significant differences were observed in larval survival or mean weight of pupae when comparing the diagonal, Z-line and multiple zig-zag dispersal patterns. Implementation of the techniques which improve larval survival and increase the weight of produced fly biomass may decrease demand for production of house fly eggs and, therefore, reduce the maintenance costs of adult colony, as well as increase the revenue earned by selling the products.