Entomologica Romanica Vol. 19 / 2014


same genera (with differently shaded pterotheca for ensuring a delayed emergence), or just one young Ecdyonurus nymph was introduced into each rearing chamber. All chambers were checked at least three times every single day: dead specimens, exuviae were removed; subimagines were transferred into small plastic salt cellars equipped with shoots of wandering jew (Tradescantia fluminensis) for ensuring the appropriate humidity for the final moult. Dead specimens, nymphal and subimaginal exuviae and the imagines were introduced into Eppendorf tubes filled with 70% ethanol. Water from the rearing chambers was not changed, but the occurring evaporation required completion of it. In case of long-term rearing experiment, biofilm covered stones were supplied at monthly intervals and represented the food source for the grazer/scraper organisms. Last instar mayflies also received periphyton. All dead and emerged specimens were identified to species level using a Hund Wetzlar stereomicroscope, an Olympus microscope and the specific literature (Bauernfeind and Humpesch 2001, Bauernfeind and Soldan 2012, Haybach 1999, Sowa 1971). Emergence success (% of subimagines (SI) emerging from reared nymphs), rearing success (% of imagines (I) in relation to the reared nymphs) and mortality in the nymphal and subimaginal stages were determined for each species. Specimens with subimaginal exuvia on the tip of one or both of their fore wings were considered sub imagines. Small Ecdyonurus individuals, which, after several careful control attempts were detected neither alive nor dead, though they were successfully introduced into the experiment, were considered dead. The suitability of the reversed funnel method for rearing of young instar nymphs in comparison with last instar nymphs was assessed with Mood ’s Median test in R statistical environment. Nymphal and subimaginal mortality, emergence and rearing success were tested for the Ecdyonurus genera datasets. Data were pooled by sampling sites in relation to sampling date. Results Rearing of last instar mayfly nymphs Though the last instar mayfly nymphs spent up to 14 days in aquatic environment, the majority of them emerged within 4-5 days after the introduction into the rearing devices. The reared individuals were distributed into 24 taxonomic units including Table. 1. Reared mayfly nymphs. 7