De terugkeer en biotoopkeuze van de Beekrombout (Gomphus vulgatissimus) in Oost-Nederland

At the beginning of the 20th century, Gomphus vulgatissimus was a moderately common species in The Netherlands. A sudden decrease occurred and the last specimen in the eastern part of The Netherlands was seen in 1925. In 1994, G. vulgatissimus was rediscovered along the Buurserbeek. More new localities were found in subsequent years (Overijsselse Vecht, Dinkel, Berkel and Slinge). The population of the Buurserbeek is probably the largest in The Netherlands, G. vulgatissimus inhabits larger streams and rivers, with a relatively high temperature and low water velocity. Most populated streams are canalised. Previous conclusions of G. vulgatissimus being a species of natural streams must be rejected. It is concluded that the recent improvement of the water quality positively influenced the expansion, of the species. Furthermore, the possible but largely unknown influence of the recent warm summers is discussed.