This paper describes microwave power absorption in an insect due to the standing-wave irradiation in free space. A method is presented to obtain the heating potential and total absorbed power in the dielectric sphere having the same electrical characteristics as those of insect. Numerical calculations on the pupae of Tenebrio molitor, which has often been used to investigate the microwave biological effects, are given in the frequency range of 1-20GHz, and the results are also discussed with respect to the exposure locations.