Abstract
1. A method is described by means of which the surface area of puparia of Drosophila melanogaster may be measured. 2. Measurement of almost 200 puparia showed that the relationship between surface area, per mg., and body weight could best be expressed in the form of the equation S=7.7049-2.1099X, where S=surface area, sq. mm. per mg. wet weight, for prepupae of mean wet weight X mg. As the standard error of estimate, ±0.117, is equal to only 2.2% of the mean surface area per mg., the surface area can be accurately estimated from the wet weight. 3. The prepupal oxygen consumption, per mg. wet weight, is shown to decrease steadily with increasing body weight; with an increase in mean wet weight from 0.847 to 1.700 mg., the oxygen consumption, per mg., decreases by about 50%. 4. Utilizing the above regression equation, the surface area of prepupae of known oxygen consumption was estimated and thus the oxygen consumption per sq. mm. of body surface. These values show no significant variation with increasing body weight, so that it can be concluded that the oxygen consumption of prepupae of D. melanogaster is proportional to the surface area.