(23(2):126-135)Biological studies of the spider mite, Tetranychus truncatus and its natural enemies

偽二點紅蟎（Tetranychus truncalus）為臺灣旱作最普遍之害蟎，對豆科植物之為害尤甚。本研究於61年3月至62年3月，在臺北室內飼養31代之記錄，各期生活史如下：卵期3~17天，平均為6.22±0.13天；幼蟎期2~17天，平均為6.25±0.38天；成蟎寫命5~29天，平均10.6±2.61天。產卵期平均為9天，一生平均可產卵60枚。各期形態均經詳細記載。偽二點紅蟎之天敵已發現13種，其中最重要而真正具有抑制力者僅小黑隱翅蟲、西方癭蠅及長毛瞞三種。 Tetranychus truncatus Ehara. is a common pest on the upland crop in Taiwan, specially infesting bean plants. In the laboratory the mites were reared and observed continuously from March 19.72 to March 1973. There were 31 generations in a year. The egg, nymphal and. adult stages were 3-17 days (av. 6.22 ± 0.13 days), 2-17 days (av. 6.25 ± 0.38 days), 5-29 days (av. 10.6±2.61 days), respectively. The female generally deposited 60 eggs within about 9 days. The morphology of each stage was described in this paper too. By the field investigation thirteen species of natural enemies were found. i. e. Stethorus hirashimai Sasaji, S. chengi Sasaji, S. ioi Sasaji, Oligota oviformis (Casey), Arthrocnodax occidentaiis Felt, Eümicromus sauteri Esben-Peterson, Scoiothrips sex-maculatus Pergande, Onus sp., Anystis sp., Bdella sp., Ambiyseius longispinosus (Evans), A. largoensis (Muma), and A. ovalis (Evans). Among them, Oligota oviformis, Arthrocnodax occidentalis and Arnblyseius longispinosus seem to be effective in checking the population of Tetranychus truncatus below economic level under the condition of without spraying insecticides for against insect pests of some hostplant in the fields