Life history, growth and secondary production of Caenis luctuosa and Cloeon simile (Ephemeroptera) in a small pond, SW France

We studied the population dynamics of the mayflies Caenis luctuosa (Burmeister) (Caenidae) and Cloeon simile Eaton (Baetidae) in a permanent pond in Southwestern France. Both species had a bivoltine life cycle. After slow and continuous winter growth, the rapid rise in water temperature in March resulted in increased growth rates until spring-summer emergence. The eggs laid by the adults of the winter generation yielded the individuals of a short summer generation in both species. The annual production values were the highest ever reported for species from both genera: 11.75 g dry weight m(-2) year(-1) in C. luctuosa and 2.05 g dry weight m(-2) year(-1) in C. simile, while P/B ratios (13 and 11.2 respectively) were similar to those reported for closely related species with bivoltine life cycles.