A migratory flight of hover-flies (Diptera, Syrphidae) observed in Austria

During an excursion sponsored by the Entomological Department of the Zoölogisch Museum, Amsterdam, to the village of Vent, Inner Oetztal, Tirol, Austria, the authors and the other participants, W. Dekkers, W. N. Ellis, Mrs. A. C. Ellis-Adam, W. van Raamsdonk, and H. J. L. T. Stammeshaus, witnessed the interesting phenomenon of a migratory flight of syrphid flies. The migration was first noticed around 9.20 a.m. on August 9th, 1967, when the senior author in the valley of the river Venter Ache near Vent saw a great number of insects flying at high speed into one direction. Under the impression at first that it concerned a nuptial flight of a large ant species, a specimen was caught in the air. When this turned out to be a hover-fly, it was at once realized that a migratory flight of these insects was going on.