1. Egg survival (ES, percentage of eggs hatched in vitro), reproductive success (RS, percentage of live young released frotn the brood ptiuch) and brood development time (d, days) in four populations of Gammarus fossarum and two populations of Gammarus roeseli were studied, in the laboratory at water temperatures of 2.(V -26.]°C. Intraspecific differences between populations were not significant, but interspecific differences were found between the two species.

Larvae of Baetis alpinus, B. lutheri and B. rhodani were reared in a stream channel (water temperature range 4.2-11.4''C) in the laboratory. The larval growth was exponential and the mean specific growth rate varied from 1.93 to 2.24% day"' for B. alpinus. 1.49 to 3.41% day"' for B. lutheri and 0.79 to 3.11% day'' for B. rhodani. These variations in growth rate were related to variations in mean temperature and this was the major factor affecting growth in the laboratory.Non-quantitative samples of the benthos in the Seebach and Unterseebach, two stony streams near Lunz, Austria, were taken at approximately monthly intervals from November 1965 to May 1968. In each year, there were two winter and three summer cohorts for B. alpinus from Seebach and two or three winter and one to three summer cohorts for B. lutheri and B. rhodani from Unterseebach. Over the study period of 30 months, eleven cohorts were recorded for B. alpinus and B. lutheri, and ten cohorts for B. rhodani. The life cycle of a cohort varied from 3 to 8 months in B. alpinus, from 2.5 to 9 months in B. lutheri and from 2.5 to 8 months in B. rhodani. Mean specific growth rate in length varied from 0.82 to 2.97% day"' for B. alpinus, 0.96 to 3.33% day'' for B. lutheri and 0.65 to 3.01% day"' for B. rhodani. The percentage of the variability in growth rate accounted for by variations in mean temperature was 63% for B. alpinus, 91% for 5. lutheri and 82% for B. rhodani. Therefore mean temperature was clearly the major factor affecting the growth rates in the field.An agreement was found between the growth rates of B. alpinus in the field and the laboratory. The growth rates o( B. lutheri and B. rhodani were slower in the field than in the laboratory at higher temperatures. The possible reasons for this latter discrepancy are discussed, and the growth rates of the three Baetis spp. are compared with those of other species of Ephemeroptera.

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1. Newly-laid eggs of Coenagrion puella (L.) from a pond near Herzogenburg (Lower Austria) were kept at constant water temperatures (range C.3.5X to c.28°C) in the laboratory. Hatching success varied with temperature; no eggs hatched below IT'C and nearly all hatched at c.l6°C. Hatching time decreased with increasing temperature and the relationship between the two variables within the range 12-28°C was well described by a power law. The length of the hatching period was less than 12 days. Hatching times estimated from the power-law equations and those obtained in the field experiments were similar. Therefore both the hatching time and the length ofthe hatching period in the field could be estimated from the laboratory data for the range 12-28°C.2. The maximum number of instars from egg to imago was 11; the average body length increment (mm) per moult was proportionately constant at c.26% and Dyar's rule was applicable. The interval between moults decreased with increasing temperature up to the seventh instar and the relationship between the two variables within the range 12-28°C was well described by a power law. The moulting interval for instars 8-11 ranged from 23 to 48 days and was relatively independent of temperature. No moulting occurred at temperatures below 12°C.3. Larval growth was logistic in the laboratory and variations in mean logistic growth rate (range 0-2.5% length day"') were related to mean temperature with no growth at temperatures < 12°C. Larval growth rates in pond experiments were similar to those estimated from laboratory data, and therefore the regression equations obtained from the laboratory experiments are probably applicable to larval growth in the field. 4. Information on the life cycle of C. puella is briefly reviewed and it is concluded that C. puella from the pond near Herzogenburg has an univoltine life cycle.