In order to study the damage of Habronema muscae (Carter, 1861) on its intermediate host, Musca domestica Linnaeus, 1758, fly larval feeding experiments were carried out. For this, a defined number of praeimaginal stages of M. domestica was transferred in daily intervals (from day 0 to day 10) on faecal samples of a naturally infected horse harboring 269 adult H. muscae in its stomach. The development of M. domestica was monitored until imagines appeared. Harvested pupae were measured and weighted and the success of infection was studied by counting 3rd stage nematode larvae in freshly hatched flies. In addition, time of pupation and duration of the whole development of the flies was noticed. Pupation, hatching and preimaginal mortality rates were calculated and the number of nematode larvae in freshly hatched flies was counted. Adult flies harboured up to 60 Habronema larvae. Lower pupal volumes and weights, lower pupation rates and higher preimaginal mortality rates were found in experimental groups with long exposure to parasite eggs compared to experimental groups with short exposure or to the uninfected control groups. Maggots of the former groups pupated earlier and fly imagines occurred earlier. These findings clearly showed a negative impact of H. muscae on the development of M. domestica. The results are discussed in connection with the destruction of adipose cells in the maggots by developing nematode larvae.
