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Abstract:
The mortality of Baetis vernus Curtis and Baetis rhodani Pictet during the terrestrial-aerial and aquatic life stages was studied at the Breitenbach near Schlitz, Hesse, Germany. The number of females emerging from the stream was recorded with emergence traps. To estimate mortality of females of both species during terrestrial life, numbers of emerging females were compared with numbers of females returning to the stream for oviposition, as shown by numbers of egg masses found in the stream. Mortality of female B. vernus during their terrestrial life stages was 98.8%. It was 91.2 and 96.6%, respectively, during the first and second generations of B. rhodani . To estimate the mortality of both sexes of B. rhodani during the aquatic life stage, the number of eggs laid by the first generation was compared with the number of adults emerging during the second generation. Mortality during the aquatic phase (both sexes combined) of B. rhodani was 91.1%.
