Studies on mosquito larval predation efficacy of some Odonata nymphs and Coleoptera larvae, abundant and widely distributed in the rice fields, were carried out in the laboratory condition, and the results are summarized as follows. 1. In Odonata nymphs, Orthetrum triangulare melania(Libellulidae) took 27.5 days of Nymphal stage through 5 times of ecdyses after hibernation, preying on total 1,414 4th instar larvae of C. p. pallens, with daily consumption of 51.6 in average and 170 in maximum. Sympetrum sp. (Libellulidae) took 21.7 days through 4 ecdyses, preying on total 457.2 larvae with daily consumption of 38.4 in average and 89 in maximum. A late instar of unidentified species of Agrionidae preyed on 20 4th instar larvae of C.p. pallens. 2. In Coleoptera, Cybister japonicus larvae(Dytiscidae) in late instars preyed on 46.6 4th instar larvae of C. p. pallens in average and 78 larvae in maximum in 24 hours, and Laccophilus sp. (Dytiscidae) larvae consumed 118.9 larvae in average and 176 larvae in maximum Hydrophilus affinus (Hydrophilidae) was the most aggressive and consumed the highest number of the larvae, showing daily consumption of 162.2 in average and 185 in maximum at the late instar.3. As both species of Dytiscidae, Cybister japonicus and Laccophilus sp. were most widely distributed and abundant in rice fields, and also potentiality of their predation efficacy was very promising. The larvae of two species would regulate the vector mosquito populations in much more degree than any other associated predators. 4. In Hemiptera, an adult of Nepa sp. of Nepidae preyed on 6 4th instar larvae of C. p. pallens in aberage and 13 in maximum in 24 hours.