An experiment was performed in which larvae of Lestes sponsa (instars 6 to 10) were maintained at constant prey density and temperature from the time they moulted into an instar until the time they moulted out of it. Prey were Daphnia magna of sizes appropriate for each instar. Lestes larvae were maintained at six prey densities, and three temperatures. The range of prey densities and temperatures used were thought to encompass the likely ranges encountered by Lestes larvae in the field. Development rates increased with prey density and temperature. There was no evidence of any trend of adaptation by any instar to any prey density/temperature combination; later instars were not better adapted to higher temperatures and earlier instars were not better adapted to lower temperatures.