Energy Transfer in Insects

Living organisms maintain a thermodynamic steady state that is far from equilibrium and thus they require a constant source of free energy. A part of this energy may be transformed or stored for short or long periods of time, but most is degraded to heat through the performance of the internal work necessary for life. The direct connection between life and the produc­ tion of heat was first convincingly demonstrated in the late eighteenth century by Lavoisier & Laplace using a simple ice calorimeter [see discus­ sion in Lusk (61), p. 33ff.]. Since then, the study of energetics (molecular, cellular, and organismal) has interested generations of biochemists and physiologists. Energetics tells us much about the conditions and mecha­ nisms responsible for vital processes and transformations within organisms. Energy considerations also have an important effect on the behavior and interaction ofindividuals and populations. But not until well into the twen­ tieth century, following the development of ecology as a rigorous discipline, was this common knowledge subjected to scientific scrutiny. The relative ignorance that exists concerning the energetics of insects is surprising, especially if one considers their numerical dominance and diver­ sity. This lack of attention at the physiological level persisted until well into the twentieth century. Researchers were more concerned with investigating human energy needs and those of domesticated animals which, with a few notable exceptions, e.g. the honey bee, are all mammals. Then too, mam­ mals, like all homoiotherms, degrade a much larger proportion of as­ similated energy to heat than do poikilotherms, so measurements of respiratory heat loss dominated the early energetics scene. .