Life-history theory predicts changes in age and size at maturity in response to constraints in animals with complex life cycles. A critical underlying assumption is that only these traits are optimized during ontogeny. However, it is not clear how altered life histories mechanistically translate into survival and fecundity. Here we present data from damselflies reared from egg to adult under day lengths mimicking the start or end (time constrained) of the season at high and low food level. These data show that an important component of immunity is suppressed under time-constrained development as well as under low food conditions and that fat storage is affected only by food availability. Intriguingly, the physiological responses are partly decoupled from age and size at maturity, which indicates that the predictive value of traits such as age and size at maturity might well be restricted.