Controlling house fly populations under laboratory conditions: Hydrotaea aenescens larvae as effective predator

Larvae of Hydrotaea are facultative predators of larvae of flies commonly found in poultry farms, chicken and pig waste, and decaying carcasses. One species, the black dump fly, Hydrotaea aenescens (Wiedemann, 1830), coexists with the housefly Musca domestica (Linnaeus, 1758) in these environments and has been employed in the biological control of the housefly in the USA and Germany. To assess the predatory efficacy of H. aenescens larvae on M. domestica larvae, we conducted controlled laboratory experiments in which we selected larvae of different sizes of the larvae and the densities of both predator and prey. We set up the experiment using adult flies from a poultry farm and reared the larvae they produced in our laboratory. Our findings indicate that second- and third-instar H. aenescens larvae effectively suppressed populations of housefly larvae under laboratory conditions, especially when the latter was smaller or the same size as the former. Under these ideal experimental conditions, a single H. aenescens larva consumed up to 29 larvae of M. domestica, potentially leading to a complete eradication of the housefly population at predator–prey density levels of 1:1 and 1:4, but only when considering both the natural mortality rate of M. domestica larvae and the additional mortality caused by H. aenescens larvae. These results corroborate a pattern previously observed in other predatory larvae and have important implications for biological control and integrated pest management programs targeting M. domestica in poultry and swine farms across South America.