Insect Metabolic Rates (original) (raw)

1 Insect metabolic rates are highly variable and are affected by acute environmental and behavioral, developmental, and evolutionary factors. 2 The effects of temperature on insect metabolic rates depend on their behavior, life-history stage, morphology, and size. In many cases, inactive insect metabolic rates increase with temperature in a manner consistent with the assumptions of the metabolic theory of ecology (MTE), but exceptions include insects that are flying, endothermic, or behaviorally thermoregulating. In these cases metabolic rates may remain constant or decrease with increasing temperature. 3 Insect metabolic rates are not generally constrained by oxygen limitation. 4 The metabolic rates for behaviorally active insects may be elevated up to 30 times greater than their standard resting metabolic rates, an aerobic scope greater than the comparable range found among similarly sized vertebrates. 5 Nutritional state can have dramatic influences on insect metabolic rates, ranging from extreme diapause in response to starvation to nearly 10-fold increases in metabolic rate following feeding. 6 Metabolic rate correlates with insect body size both intra- and interspecifically. The interspecific slope is ¾, as predicted by MTE. Individual insects as well as eusocial insect colonies share common hypometric scaling exponents, but there is extensive variation in the metabolic elevation (i.e., scaling intercept or normalization constant) of these allometric relationships. While some of this variation may be related to methodology and behavioral variation, it is likely that these patterns may reflect previously unrecognized evolutionary differences in physiology and life history. 7 Future extensions of MTE should include physiological, behavioral, and evolutionary mechanisms. Future developments of MTE have great potential to investigate a number of areas in which further research is in highly needed including the evolution of insect endothermy, body size, eusociality, and metabolic symmorphosis.