Miura T, Takahashi R M, Stewart R J
University of California Mosquito Control Research Laboratory, Parlier 93648.
J Am Mosq Control Assoc. 1990 Sep;6(3):490-5.
Estimates of relative and absolute density in rice field populations of damselfly nymphs (predominantly Enallagma civile with few Ischnura denticollis) were compared using the regression method. An equation, X = Y divided by 0.0016, allows estimation of absolute density (X) from a relative density index (Y, dipper count). In the rice growing area of Fresno, California, nymphal population peaks appeared during June and August approaching 3-5 million per 0.405 ha (1 acre). Spatial distribution was theoretically represented fairly well by a negative-binomial distribution. The degree of clumping is one of overdispersed types; it is especially classified as a model of randomly distributed colonies with mean colony size fixed. Presence or absence of submerged vegetation markedly affected damselfly nymphal density but the biomass of submerged or emerged vegetation was not a significant factor.
采用回归方法比较了稻田豆娘若虫（主要是普通色蟌，有少量齿突色蟌）种群的相对密度和绝对密度估计值。方程X = Y除以0.0016可根据相对密度指数（Y，舀取计数）估算绝对密度（X）。在加利福尼亚州弗雷斯诺的水稻种植区，若虫种群高峰出现在6月和8月，每0.405公顷（1英亩）接近300万至500万只。理论上，空间分布用负二项分布能较好地表示。聚集程度属于过度分散类型之一；它尤其被归类为平均菌落大小固定的随机分布菌落模型。沉水植物的有无显著影响豆娘若虫密度，但沉水或挺水植物的生物量不是一个重要因素。
