Survival period, pattern of decrease in body weight and metabolic rate under starvation conditions were examined to clarify responses to starvation of a predatory insect, the mantis, Paratenodera angustipennis (S.). (i) The average survival period in starved condition was the shortest in the 1st instar larvae (5.4 days) and the longest in the adults (15.0 days for males, 26.7 days for females). (ii) The body weights of the 3rd and the 5th instar larvae decreased almost linearly during fasting period, whereas those of adults decreased greatly during the initial 5 days, and then exhibited little further decline until their death. (iii) The carbon dioxide production by the adult mantids in the dark condition at constant 26°C was measured by the improved Boysen-Jensen's method. There was a linear relationship between the body weight and the metabolic rate per individual on a double logarithmic scale, and the regression coefficient b was 0.806. (iv) The metabolic rate per individual was greatest at satiation, but the rate per unit weight was maximum on the 5th day after satiation when the food had been just digested completely, and both decreased with the progress of starvation. (v) Based on the above mentioned results, properties of P. angustipennis as a predator were discussed.