Occurrence of carabid beetles (Coleoptera: Carabidae) in cabbage fields and their possible impact on lepidopteran pests

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The species assemblage and seasonal activity of carabids were investigated in a cabbage field, an adjacent fallow field, and the field boundary during 1994 and 1995 by pitfall trapping. Trap catches indicated that Amara and Harpalus species were generally active in every habitat during the 1st (May to July) and 2nd (August to September) growing seasons, respectively. Small species such as Bembidion morawitzi Csiki were active in the 3rd growing season (November to March), especially in the cabbage plot. The adults of the beneficial species Chlaenius micans (F.) were active in the 1st and 2nd growing seasons and their larvae were found on cabbage heads in the 1st growing season. The adults of another beneficial species, Campalita chinense (Kirby), were active in the 2nd growing season; the larvae were trapped during the 1st and 2nd growing seasons. Although the seasonal activity patterns of these beneficial species varied spatially and temporally, they consistently preferred the cabbage plot to the boundary. The timing of the peak activity of the beneficial species coincided to some extent with the peak density of lepidopteran larvae. The activity pattern of the beneficial carabid species could enhance their value as biological control agents for cabbage pest insects.