The two species of rice bugs causing pecky rice, Cletus punctiger and Cletus schmidti are often observed coexisting in the rice fields of nearby fallow land. Direct feeding damage to rice by C. punctiger and C. schmidti can lead to a reduction in grain quality and quantity. These studies were carried out to investigate the development of C. punctiger and C. schmidti at various constant temperatures ranging from 20 to 30℃, 65% RH, and a photoperiod of 16L:8D. Egg hatchability of C. punctiger/C. schmidti at the temperatures of 20, 25 and 30℃ were 80.6/88.0, 91.7/96.3, 96.4/96.2 %, respectively. The development periods of eggs of C. punctiger/C. schmidti at the temperatures of 20, 25, and 30℃ were 16.4/18.4, 9.4/10.2 and 6.4/7.3 days, respectively. Mean developmental periods of lst, 2nd, 3rd, 4th and 5th nymphs of C. punctiger/C. schmidti at 30℃ were 2.1/2.0, 3.5/4.0, 3.3/5.6, 3.2/4.8 and 5.8/6.9 days, respectively. Oviposition began 8.1 days after emergence at 25℃, and the longevity of female and male were 120.0 and 117.3 days, respectively. Total number of eggs through the life of female were 245.5 laying 2.2 eggs a day in average at 25℃. The development periods of egg and nymphs of C. punctiger were relatively shorter than those of C. schmidti. Availability of male had affected the egg hatchability greatly that laid at 30th day after 60 days period of oviposition in the presence of adult male of C. punctiger. The fertile eggs laid by the female together with male was 92.1% but those without male was only 9.6%.