Effect of Load Carriage on the Respiratory Metabolism of Running Worker Ants of Camponotus herculeanus (Formicidae)

The influence of load carriage on the metabolic rate of running worker ants of Camponotus herculeanus (L). was investigated by measuring the CO2 liberation of unloaded and loaded running individuals and by determining the RQ under different conditions. Further, some preliminary experiments on the capability of different ant species of carrying loads were carried out. The RQ of running ants was significantly different from that of anaesthetized animals, being 0.91 and 0.86 respectively. The metabolic rate per unit weight of loaded running individuals was a linear function of the load up to 55 mg, which is 1.4 times the mean weight of the ants. The net cost of transport per unit of total weight (J g1l km') was independent of how the weight was divided between the ant and the load. The extra cost of load carriage, net cost of loaded minus net cost of unloaded running, was insignificant for small loads. Finally, the load carrying capacity of different ant species was related to morphological features, especially the length of the legs.