Foraging swarms of Spotted darter (Sympetrum depressiusculum)

On three evenings of extremely hot days in July of 2018 and 2019 large groups of high-flying Spotted Darter (Sympetrum depressiusculum) were encountered in the Woldlakebos in the northwest of Overijssel. These swarms were not migrating but stationary. They were foraging on little insects that under these weather conditions were able to fly high.

Mass flight of foraging Sympetrum depressiusculum in Woldlakebos (Weerribben-Wieden) at 8:15 PM on 25 July 2018. Red arrows indicate the flight direction. Photo: René Manger