Insects of a small aestival stream in northern Sweden

Abstract

The insects of a small and cold aestival stream in northern Sweden were studied from semiquantitative kick-samples taken every ten days throughout the ice-free season in 1987. The stream froze solid at least in some sections in some winters. In addition to dipterans that were only identified to the family level, five ephemeropteran, four plecopteran, 11 coleopteran (Dytiscidae), and four trichopteran (Limnephilidae) species were found. Baetis bundyae Lemkuhl, Heptagenia orbiticola Kluge (Ephemeroptera), Nemoura cinerea (Retzius) (Plecoptera), Hydroporus palustris (L), Agabus setulosus (J. Sahlberg) (Coleoptera), Anabolia concentrica (Zetterstedt), Limnephilus coenosus Curtis, and Micopterna sequax McLachlan (Trichoptera) were all common. Malaise trap data are given for Plecoptera. The two ephemeropteran species Heptagenia orbiticola and Metretopus alter Bengtsson, and the plecopteran species Nemoura viki Lillehammer were recorded for the first time in Sweden. The remarkable species composition was attributed to the harsh abiotic and poorly studied environment. We predicted that the larval composition of this stream was representative for aestival streams in northernmost Fennoscandia.