Respiratory Q10 varies between populations of two species of Myrmica ants according to the latitude of their sites.

Metabolic respiration by groups of resting Myrmica ruginodis and M. scabrinodis worker ants from five sites representing a range of latitudes, have been compared by measuring rates of CO(2) production-standardised by fat-free weight-at 5 and 25 degrees C. M. ruginodis which lives in cooler habitats than M. scabrinodis consistently produced more CO(2). At 5 degrees C ants of both species from southern latitudes were metabolically more active than those from more northerly latitudes, whereas at 25 degrees C the situation was reversed. Estimates of Q10 were positively correlated with latitude indicating that the respiratory metabolism of northern populations increases relatively more in response to rising temperatures than southern populations. Values of Q10 at different latitudes were the same for both species. The results are discussed in terms of seasonal fluctuations of temperature at different latitudes.