Abstract.1Instar 10, 11 and 12Ischnuralarvae were maintained throughout the instar on a constant food supply (Daphnia magnaof a standard size).2A very narrow range of prey availability separated cohorts in which all the larvae successfully moulted to the next instar, from those in which all the larvae died (less than oneDaphniaper day in the case of instar 10).3Larvae were able to survive long periods without food at 16°C.4Prey availability had a marked effect on development rates, which continued to increase at prey densities well in excess of 100% survival by the larvae.5The data onIschnurasurvival and development rates are compared with previously published general models of these two components of the predators' rate of increase.6We conclude that starvation is very unlikely to be a significant cause of mortality in the field forIschnura(or indeed most other Odonata larvae), but that prey availability undoubtedly influences development rates. Natural selection should therefore favour larvae that forage optimally to minimize development times