An isolated locality of Somatochlora arctica (Zett.) in Limburg, Belgium (Anisoptera: Corduliidae)

On 28-V1I-I978, amale, S. arctica was captured in a Sphagnum bog near Koersel by G. Lejeune and J. Burny. The specimen was photographed but released. A female was also observed. On I Aug. a male was captured and collected by A. Anselin. A female ovipositing and a third one (sex unknown) were seen. These records were the first since 1964, the end of the most important observation period of this species in our country. Some more recent data from G. Janms (July 1982) and G. Jannis and N. Michiels (July and August 1983) prove that the population is still present. The Sphagnum bog is situated some 10 km NE of Koersel, in the western part of the province of Limburg, Belgium, at an altitude of 60 m. It is surrounded by a mixed forest (Betulo-Quercus and Pinus) in the valley of the "Zwarte Beek", a brook which takes its source on the Campine plateau and discharges into the River Demer (Scheldt-basin) The region consists of large heather fields with Calluna vulgaris, open sand dunes and pine forests, with several water bodies (natural and artificial), mostly mesptrophic. A more detailed description is given by R. NIJS (1978, De inbreng van de landschapsekologie in de ruimlelijke planning met een facetstrukluurschels voor hel beekdallandschap "De Zwarle Seek " (West-Limburg) ah type sludie, Thesis HISROO, Gent). The bog has a surface of some 0.30 ha and consists of two different parts: the shallower Sphagnum-part, which is mesotrophic and has a typical vegetation of Drosera intermedia, D. rotundifolia, Rhynchospora fusca, R. alba. Narthecium ossifragum. Eriophorum angustifolium. Oxycoccus palustris and Erica tetralix, and a more eutrophic and deeper part with Potamogeton polygonifolius. willow shrubs and Typha latifolia and on the borders some Molinia coerulea. The insects were flying mostly over the Sphagnum-part, where the damselflies Ceriagrion tenellum (De Vill.) and Lestes sponsa (Hans.) were very abundant. Aeshna juncea( L.) and Sympetrum danae (Sulz.) were also observed.