The influence of thermal history on temperature-dependent flight performance was investigated in an invasive agricultural pest insect, Ceratitis capitata (Diptera: Tephritidae). Flies were exposed to one of four developmental acclimation temperatures (T acc : 15, 20, 25, 30°C) during their pupal stage and tested at these temperatures (T test ) as adults using a full-factorial study design. Major factors influencing flight performance included sex, body mass, T test and the interaction between T test and T acc . Successful flight performance increased with increasing T test across all acclimation groups (from 10% at 15°C to 77% at 30°C). Although T acc did not affect flight performance independently, it did have a significant interaction effect with T test . Multiple comparisons showed that flies which had been acclimated to 15°C and 20°C performed better than those acclimated to 25°C and 30°C when tested at cold temperatures, but warm-acclimated flies did not outperform cold-acclimated flies at warmer temperatures. This provides partial support for the 'colder is better' hypothesis. To explain these results, several flight-related traits were examined to determine whether T acc influenced flight performance as a consequence of changes in body or wing morphology, whole-animal metabolic rate or cytochrome c oxidase enzyme activity. Although significant effects of T acc could be detected in several of the traits examined, with an emphasis on sex-related differences, increased flight performance could not be explained solely on the basis of changes in any of these traits. Overall, these results are important for understanding dispersal physiology despite the fact that the mechanisms of acclimation-related changes in flight performance remain unresolved.

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·CO2 ratio) showed a marked increase in grouped caterpillars, particularly in larger groups. Other benefits of aggregation (e.g. reduced predation or increased growth rates) likely outweigh these potential costs, because individuals of E. capensis aggregate voluntarily despite no obvious energetic or hygric advantage, and other potentially confounding group effects (e.g. increased thermoregulatory advantage or whole-animal activity) are inconsequential. The results of this study provide an important exception to physiological studies reporting enhanced energy or water conservation in animal groups. Supplementary material available online at

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