Mass swarm of a grass fly in Keszthely, Hungary

This study aimed to identify the small flies which occurred in disturbingly high numbers covering the upper floors' windows of the Georgikon Campus of the Hungarian University of Agriculture and Life Sciences in the early fall of 2021. During the on-site visit, numerous specimens were collected for later identification. As a result of the species determinations, Thaumatomyia notata (Meigen, 1830) was identified. According to the employees, the mass autumn appearance of flies in that high building has been repeatedly seen over the past decades. Thaumatomyia notata is, in fact, a valuable species, of which larvae are primarily found in the soil as a predator of Pemphigus spp. root aphids