[An experimental study of the flight path orientation of Hybomitra horseflies (Diptera: Tabanidae) under field conditions].

Examined specimens of horseflies flew out of 3 start points disposed on the water surface of the lake, about 250-300 m from the coast line (I start point), 90 m (II start point), 20 m (III start point). This position of start points minimised the number of topographic landmarks for the horseflies and gave the possibility for a visual monitoring of flight trajectories. In favorable weather circumstances for the flight (17-22 degrees C, wind 0-1 m/sec, cloud 0-5%) the majority of horseflies demonstrated the flight trajectories to the most close points of the coast. The lesser favorable weather circumstances (16-17 degrees C, wind 3-5 m/sec, cloud 60-100%) decreased the number of horseflies flying to far points of the coast line; unfavorable weather circumstances (16-17 degrees C, wind 5-8 m/sec, cloud 80-100%) almost completely suppressed the flight activity on I start point and decreased it on II and III start points.