The life cycles of three species of Ephemeroptera in two streams in Poland

Abstract

Nymphs of Rhithrogena iridina, Baetis alpinusand Baetis melanonyx were collected in theWolosatka and Terebowiec streams; Bieszczady NationalPark, southeastern Poland. The streams have differentenvironmental conditions. The life cycles of Rhithrogena iridina in the Wolosatka and theTerebowiec streams were of the univoltine winter type.In the Wolosatka (Station 1) this species had aunivoltine life cycle with one cohort. In theTerebowiec (Station 2), R. iridina had aunivoltine life cycle with two cohorts – winter andsummer. The development of Baetis alpinus tookvarious courses depending on environmental conditions.At the lower station (Wolosatka), where watertemperature reached higher values and the stream bedis less shady, the species had a winter-summer cyclewith two generations a year. At the higher station,(Terebowiec) it likely had a winter cycle with one ortwo generations. Baetis melanonyx had summercycles with one generation at both stations.