The "hotter is better" hypothesis states that the rate-depressing effects of low temperature cannot be compensated by acclimation or adaptation. In the present study we test this hypothesis by using metabolic rate and aerobic scope as performance indicators. Madagascar hissing cockroaches (Gromphadorhina portentosa) were acclimated to different temperatures for several weeks. After this acclimation period resting and maximal metabolic rates (RMR and MMR respectively) were measured via flow-through respirometry at temperatures ranging beyond the acclimation temperatures. RMR was obtained from animals kept in a dark chamber, at a given temperature, for at least 40 min. Following 1 min of vigorous shaking, MMR was calculated by using the highest continuous 30-sec running average of metabolic rate. Aerobic scope was determined as the difference between MMR and RMR. Preliminary results indicate that while the thermal reaction norms for RMR of cold acclimated animals are left-shifted compared to those of warm acclimated ones, the reaction norms for MMR displayed a reverse pattern, resulting in the warm acclimated animals having a higher aerobic scope. If confirmed, these results would lend support to the hotter is better hypothesis but also raise questions concerning the perception of metabolic rates as performance traits.