A comprehensive study on daily pupal weight loss due to histolysis and histgenesis in Bombyx mori Linn., has been undertaken. The percentag of pupal weight loss in the male pupa is higher than the female, conforming that the female pupa require more energy in the form of less pupal weight loss for ovipositional activities. The regression equation clearly shows higher percentage loss of daily pupal weight in male than female with respect to age and, this is also evident from the slope of the regression line. Moreover, analysis of the coefficient of correlation shows that the weight loss of pupa is directly correlated with the age rather than climatic parameters under which the pupa dwells.