Standard energy metabolism of a desert harvester ant, Pogonomyrmex rugosus: Effects of temperature, body mass, group size, and humidity.

Pogonomyrmex rugosus (Hymenoptera: Formicidae) is an important seed predator in the Mojave Desert of the southwestern United States. Its standard rate of O(2) consumption ( Vo(2)) varied significantly with temperature ( Vo(2) = 10((-1.588 + 0.0315T)), where Vo(2) is ml.g(-1).hr(-1) and T is body temperature in degrees C). The ratio of the Vo(2) values at 10 degrees C increments in body temperature, Q(10), also varied with temperature; methods of calculating Vo(2) from temperature with a shifting Q(10) are described. Vo(2) also varied with body mass ( Vo(2) = 0.0462M(0.669), where Vo(2) is ml.hr(-1) and M is body mass in g). Vo(2) was inversely related to relative humidity and was independent of group size. The rise in Vo(2) at low relative humidities was caused by increased activity and resulted in higher rates of net water loss. The primary metabolic adaptation to xeric conditions in P. rugosus appears to be a lower-than-predicted metabolic rate.