In the first part of this work, the influence of water temperature on egg development and on the different phases of the embryonic development of the Siphlonurus aestivalis is demonstrated. The warmer the water during the oviposition, the faster the diapause begins. This diapause stops when the water temperature becomes colder, but the longer the diapause, the longer the cold period has to be. The availability of food is the main parameter influencing larval growth. Larvae eat sediment, consuming simultaneously diatoms and detritus.
Diatoms are more energy-giving than detritus, and so are responsible for larval growth.
Diatoms concentration available in the biotope has an influence on the growth rate of the larvae, on their size at maturity and consequently on the fecundity of females since the number of eggs is related to their size, and on the accumulated reserves. Analysis of nymphs, subimagos and imagos of 4 mayfly species showed that reserves accumulated during larval development are essentially lipids plus a very small amount of glycogen. Glycogen is consumed during the subimago emergence and at the beginning of the adult flight. Lipids maintains the basic metabolism of species with long-life winged stages and serve as the main fuel consumed during flight. This trade-off is particularly well illustrated by the two female morphs in Dolania americana.