Furthermore, higher Hsp70 levels are associated with reduced growth rates. Altogether, this suggests that the proposed physiological cost of rapid growth in terms of reduced cold resistance may be mediated through reduced expression of Hsp70 in fast growers. The overall aim of the present study is to evaluate physiological costs of rapid growth in terms of reduced cold resistance, as measured by chill coma recovery times, both at the individual and at the population level using the damselfly Ischnura elegans as a model system. At the population level we compared two northern univoltine with two southern multivoltine populations. Given the stronger time constraints associated with multivoltinism, we expected higher growth rates in the southern populations. Based on previous empirical research we expected lower cold resistance in the southern populations, and rapid growth to be associated with reduced cold resistance potentially through a link with lower Hsp70 levels. Because patterns in growth rate and cold resistance among populations along latitudinal Orbifloxacin gradients may depend on rearing temperature, we reared larvae at three temperatures from the egg stage in a common-garden experiment. Clear latitudinal patterns in growth rate were observed. This relationship was consistent with differences in Hsp70 levels at the population level. This temperature range has been shown to generate clear thermal reaction norms in related species and spans the natural temperature regime of the populations of this species during the largest part of the growth season. Furthermore, survival is low when larvae are reared at lower and higher temperatures. We collected 8–10 females for each of four study populations. Field-collected females were placed individually in small plastic containers and given wet filter paper as oviposition substrate and allowed to oviposit for three days in the laboratory. Afterwards they were released in the field. Rearing experiments were performed with the permission of the Flemish Agency of Nature and Forestry. Filter papers with eggs were transported to Belgium where they were kept at 21uC. At the day of hatching,Olsalazine Disodium larvae were randomly divided among six identical incubators set at 18uC, 21uC and 24uC. Each larva was placed individually in a circular plastic 180 ml cup filled to a height of 5 cm with aged dechlorinated tap water. Cups were rotated daily within the incubator and regularly between the incubators of the same temperature treatment. Larvae were daily fed ad libitum with brine shrimp nauplii. When larvae entered the final instar the daily food ration was doubled. We daily checked animals for adult emergence. Development time was calculated as the number of days between egg hatching and adult emergence.