Abstract: The population dynamics and distribution of the rice water weevil, Lissorhoptrus oryzophilus Kuschel, was investigated in the first cropping rice field by direct sowing in a small flatland of mountainous area in Xiangshan, Zhejiang Province. The density peak of adults hibernated on hillside and field ridge occurred concurrently in early May. These adults migrated directly into rice field about 7 days after feeding on weeds and the immigrant peak of the direct seeded rice field appeared. They showed distinct preference of feeding, distributing and ovipositing for the habitat with water. In the direct seeded field, the nearer to the ridge, the higher density of the weevil population was, and the weevil density was higher in the margin than that in the middle in the same row. In the direct seeded rice field, it took the weevil about 50 days to complete its development of the first generation, the weevil multiplied 7.23-fold, which was significantly lower than that in the transplanted rice field, and mainly attributed to lower oviposition per adult in the direct seeded rice field. The weevil adults of the 1 st generation migrated back to the hillside or the ridge of the field for over-summering or over-wintering at the end of July. Some suggestions for the pest forecast and control were also brought forward based on the characteristics of the pest population dynamics and distribution in the direct seeded rice field.

Key words: Lissorhoptrus oryzophilus, direct seeded rice, population dynamics, distribution, feeding, reproduction

摘要： 对浙江省象山县山谷小平原直播稻区的稻水象甲种群动态和田间分布进行了系统调查。稻水象甲成虫在山坡地和直播稻田埂等越冬场所出蛰后取食杂草，并于5月初同期出现成虫高峰。这些成虫约7 d后直接迁入直播稻田，形成直播稻田稻水象甲的迁入高峰。稻水象甲在直播稻田的取食、产卵和分布表现出明显的喜水习性。在同一丘直播稻田内，离田边越近，越冬代成虫和一代卵、幼虫、茧蛹的数量越大；在同一畦内，畦边多于畦中。稻水象甲在直播稻田完成一个世代约需50 d，增殖倍数（一代成虫峰值/越冬代成虫峰值）为7.23，明显低于移栽稻田，主要原因是稻水象甲在直播稻上的产卵量较低。7月底一代成虫向山坡地和直播稻田埂等越夏越冬场所回迁。根据直播稻区稻水象甲种群动态和分布特点，提出了相应的虫情调查和测报防治建议。

关键词: 稻水象甲, 直播稻, 种群动态, 种群分布, 取食, 繁殖