The pattern of heat generation, the thermogram, of an insect has two kinds of components: the steady state or basal metabolic rate heat generation, and heating and cooling transients. Microcalorimeters have been constructed to determine the thermogram for individual insects, including the mosquito, Aedes aegypti and the cockroach, Blatella germanica. The instruments have a calorimeter constant, or figure of merit, of p μw power from the sample/μvol signal output. They provide for air exchange and CO2 exhaust, which is necessary for long term scans, lasting for 6-30h. The results of some basic experiments in feeding, in anesthetization, and in microbial infection indicate that microcalorimetry of individual insects may be a practical means for monitoring the results of such experiments. The insect is confined in a glass vessel, but otherwise is not restrained. The magnitudes of some of the contributions to the insect thermogram may be rationalized in a simple way, by using the estimated specific heats of metabolism and of water evaporation. The observed heats also compare roughly with those estimated from oxygen respirometry. Integration of the heating and cooling transients over longer periods of time lead to estimates of the amount of material turnover (nutrient, water) involved in maintenance of the individual insect.
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Acknowledgements--This work was supported by NIH Grants GM18807-5 and AI09914, and by the University of Minnesota Graduate School. This is Paper No. 10044, Scientific Journal Series, of the Minnesota Agricultural Experiment Station.