SUMMARY Animal construction allows organisms to cope with environmental variations but the physiological costs of such behaviour are still poorly understood. The aim of the present study was to measure the physiological cost of construction behaviour through the oxidative balance that is known to affect the ability of organs to function, stimulates senescence processes and ultimately impacts the fitness of the organism. We used larvae of caddisfly, Limnephilus rhombicus , by experimentally modifying the effort associated with case building. Larvae that were forced to build a new case showed a significant increase in both total antioxidant capacity and the specific activity of superoxide dismutase 48 and 72 h, respectively, after the initiation of the reconstruction. These results strongly suggest that the larval construction behaviour triggered the production of reactive oxygen species, but their effects were reversed 7 days after the reconstruction. In the animals that were forced to build a new case, oxidative stress appeared to be mitigated by a network of antioxidant defences because no oxidative damage was observed in proteins compared with the control larvae. At the adult stage, while longevity was not sex dependent and was not affected by the treatment, body mass and body size of adult males from the reconstruction treatment were significantly lower than the control values. This unexpected sex effect together with data on oxidative stress highlights the difficulty of determining the physiological cost associated with energy-demanding behaviours, implying a consideration of both their energetic and non-energetic components is required.