ated the impact of the factors affecting the efficacy of H-traps. Catching data of 15 H-traps were analyzed. The traps were deployed at an outdoor equestrian paddock (Sántos, Somogy county) from May to July 2018. In twelve weeks, the traps collected 10,556 horsefly specimens, dominated by Tabanus autumnalis and Haematopota italica. In the first experiment we found that the distribution of caught individuals was inhomogeneous among the samples. According to the amount of caught individuals, trap efficacy showed spatial and temporal inhomogeneity. In the second experiment, after the rearrangement of traps, we found that traps placed in open, sunny places in the centerline area caught significantly more horseflies than those in shady border regions. It can be concluded that the positioning of H-traps in sunny areas significantly enhances their tabanid-catching efficacy.