Full-text - Norsk entomologisk forening

+ Light 'rapX Emergence 'rapst Malaise 'raps~0,5 1 kmFig. I. A map showing the sampling sites at the Raubekken.Blesbekken and the Driva. The highest sitesampled in Blesbekken was 1350 m a.s.l.depth of 5- 10 cm. Successively the net wasmoved upstream until a stretch of 1. 5- 2.0 m ofthe bottom of the stream was covered. Fromeach stream 3-4 litres of bottom substrate weretaken to the laboratory and sorted under a microscope.During the years 1978 -1981 between10 and 20 emergence traps of the tent typewere operated in the Raubekken and Blesbekken.Each trap covered 0.25, 0.5 or 1.0 m2.Three Malaise traps were working during thesummers of 1980 and 1981 at each of thestreams. A light trap was in use in the years1973 - 75 on the bank of the Driva which is themain river in the valley, and into which the Raubekkenand Blesbekken empty (Fig. 1). The severaltraps for collecting adults were emptiedonce a week during the whole flight season ofTrichoptera.Larval instars were separated by head widthmeasurements.Chemical characteristics of the water in the2A~/~.r:?