De Bandheidelibel (Sympetrum pedemontanum) in Overijssel

In The Netherlands Sympetrum pedemontanum (Allioni, 1766) is a very rare species. Only a few populations in the south of The Netherlands were known since the eighties, mostly in nature reserve areas. In 1996 and 1997 an influx occurred and individuals of S. pedemontanum have been recorded at about 20 places all over the country. This paper describes the discovery of three new populations in the eastern part of The Netherlands since 2000. In August 2000 a new population of S. pedemontanum was discovered along the Soestwetering (near Holten) in the southeast of the province Overijssel, An extensive survey of all streams and waters in the surrounding agricultural area (about 90 km2) was done, to describe the whole population. Results showed that in at least 34 km2 individuals of S. pedemontanum were present. Most of the populated streams were slow moving and well vegetated including a rich riparian component. On average, the water quality was rather euthropic or mesotrophic and was influenced by seepage. Most likely, this settlement is a result of the 1996/1997 influx. However, the area in which the new population of S. pedemontanum was discovered, was visited between 1997 and 2000 several times and S. pedemontanum was not seen during these visits. In addition to the discovery of 2000, two new populations of S. pedemontanum were discovered in 2002 in the north of the province Overijssel approximately 30 km north of the first site. One population was situated in a newly developed nature reserve called ‘De Horte’ near Dalfsen and is surrounded by agricultural area. The stream in which S. pedemontanum is present is slowly moving and has a width of 2-8 m. The second population was discovered near Lichtmis and is also situated in agricultural area. Here, S. pedemontanum inhabits a very narrow stream with a good water quality. It is concluded that after the settlement in 1996 and 1997 S. pedemontanum has taken advantage of the improving water quality in the province of Overijssel. The expansion was facilitated by the species known capacity of wandering.