Metabolic rate determines an individual's rate of resource acquisition, assimilation, growth, survival and reproduction. Studies involving a broad range of taxa and body sizes typically result in whole-organism metabolic rate scaling to the ¾ power of body mass. Competing models have been proposed to explain this allometric relationship. The nutrient supply network model of West et al. (1997) proposes that the ¾ power relationship results from the fractal nature of space-filling nutrient supply networks. The model of Kozlowski et al. (2003) proposes that the scaling of metabolic rate with body mass will vary from 2/3 to 1 among different taxa, depending on the degree to which increasing body size depends on increasing cell size or number. The present study measured resting metabolic rates across a broad range of body sizes in nymphs of Melanoplus sanguinipes F. and also analyzed published reports of metabolic rates in adult Orthoptera. The two sets of data were in close agreement: the scaling exponent for the ontogenetic series of M. sanguinipes was 0.92, and for the interspecific, phylogenetically corrected regression with adult Orthoptera, was 1.06. Both scaling exponents were significantly greater than the 0.75 predicted by the nutrient supply network model.