|Sympetrum nigrescens||Libellulidae||Highland Darter|
Species account: this species has been described as distinct from the Common Darter. It is supposedly found in extreme west and north of Europe in Ireland, Scotland and Norway. The reliability of the characters have been questioned and it is treated in most publications as a form of S. striolatum.
Range: north western Europe. Specimens reported to conform to this taxon have been reported from western Ireland, north-west Scotland, south-western Norway and Åland Islands in Finland.
Determination of adults: this taxon was described by Lucas on basis of colour differences from striolatum. S. nigrescens was later downgraded by Lucas to a subspecies of striolatum and synonomised with nigrifemur Selys 1884 described from Canaries and Madeira. Both nigrescens and nigrifemur were redescribed as distinct species by Gardner (1955) based on differences in genitalia in Scottish specimens. The distinguishing characters from other Sympetrum species especially S. striolatum given by Gardner (1955) are repeated in Askew (1988). More recent authors have disputed the status of nigrescens as a separate species as the characters are not as reliable as Gardner states. Individuals with intermediate characters have been reported from Finland and Ireland (Hämäläinen 1985; Merritt and Vick 1983).
Determination of larvae: larvae are reportedly distinct (Gardner 1955). The species is keyed in Askew (1988), which figures whole larva and characterising features.
|Nelson, B., Thompson, R. & Morrow, C., 2000 (May 2). [In] DragonflyIreland http://www.ulstermuseum.org.uk/dragonflyireland/|