Pitcairn M J, Wilson L T, Washino R K, Rejmankova E
Department of Entomology, University of California, Davis 95616.
J Med Entomol. 1994 Jul;31(4):545-53. doi: 10.1093/jmedent/31.4.545.
Spatial patterns of Anopheles freeborni Aitken and Culex tarsalis Coquillett larvae were studied during summer by sampling with a standard mosquito dipper in 104 rice fields in northern California. Culex tarsalis larval abundance was highest initially, then decreased and remained low through late summer. An. freeborni larval abundance was low initially, increased steadily, and peaked in mid-August. The degree of aggregation for both species as measured using Taylor's power law and Iwao's Patchiness Regression was highest among the first instars and then decreased as the larvae aged. Seasonal peaks in the degree of aggregation were observed. Analysis of covariance showed that for Taylor's model both instar and time effects were statistically significant, with instar showing the largest effect. In comparison, all slopes resulting from Iwao's model were significantly different, indicating that this model was affected by specific combinations of instar, week, and location and, thus, was less useful in developing an area-wide sampling plan. Optimal sample size was estimated using two methods. One method calculated the number of dips needed to estimate population abundance at three fixed-precision levels. The second calculated the minimum number of dips needed to collect at least one larva. The latter requires a substantially smaller sample size and may provide an effective method for monitoring larval mosquito abundance for control purposes.
夏季期间，通过使用标准蚊虫采样勺在加利福尼亚州北部的104块稻田中进行采样，研究了弗里博恩按蚊（Anopheles freeborni Aitken）和尖音库蚊（Culex tarsalis Coquillett）幼虫的空间分布模式。尖音库蚊幼虫的丰度最初最高，随后下降，并在夏末一直保持在较低水平。弗里博恩按蚊幼虫的丰度最初较低，随后稳步增加，并在8月中旬达到峰值。使用泰勒幂法则（Taylor's power law）和岩尾斑块回归法（Iwao's Patchiness Regression）测量的两种蚊虫的聚集程度在一龄幼虫中最高，随后随着幼虫的生长而降低。观察到聚集程度的季节性峰值。协方差分析表明，对于泰勒模型，龄期和时间效应在统计学上均具有显著性，其中龄期的影响最大。相比之下，岩尾模型得出的所有斜率均存在显著差异，这表明该模型受龄期、周数和地点的特定组合影响，因此在制定区域范围的采样计划时用处较小。使用两种方法估计了最佳样本量。一种方法计算了在三个固定精度水平下估计种群丰度所需的采样勺数量。第二种方法计算了收集至少一只幼虫所需的最小采样勺数量。后者所需的样本量要小得多，可能为监测用于控制目的的蚊虫幼虫丰度提供一种有效的方法。
