在进行田间昆虫种群数量的研究工作中,要正确地估计出该种昆虫种群在其种作物田内的总体数,或它对某种作物的为害程度时,比较经济和有科学依据的办法是应用抽样方法。因为抽样理论不仅可以告诉我们对被研究对象的适当抽样数量,而且还可告诉我们抽样估值的误差情况,这样就使研究质量有了保证。但如何能准确地反映出被研究对象的实况,和保证抽样指标与总体中同一指标的标准离差为最小,则除对被研究对象的生物学特性有一定的了解外,必须熟悉抽样的理论,然后根据这些知识才能确定采用适合于它的抽样方法。 抽样的方法,按组织方式的不同,一般可分为下列几种: 1.简单随机抽样法(或称纯随机抽样法); 2.分层抽样法(或称典型抽样法、分区抽样法); 3.集团抽样法(或称成组抽样法); 4.二阶抽样法; 5.双重抽样法。 在上述每种抽样法中,又分为无放回抽样与有放回抽样两种,前者又称不重复抽样,后者称为重复抽样。由于抽样时是用随机抽取,而随机抽取的方法,室内常用的是抽签法或随机数表。田间在昆虫方面所常 In conducting research on the number of field insect populations, it is more economical and scientifically justifiable to correctly estimate the overall population of the insect population in its crop field or its degree of damage to a crop Sampling method. Because sampling theory not only tells us the appropriate number of samples to be studied, but also tells us the error in sampling estimates, thus ensuring the quality of the study. However, how to accurately reflect the actual situation of the subject and ensure that the standard deviation of the same indicator among the sampled indicator and the whole body is the minimum, then besides the biological characteristics of the subject, some knowledge must be familiar with the theory of sampling , And based on this knowledge can we determine the sampling method that is appropriate for it. Sampling methods, according to the different ways of organization, can be divided into the following categories: 1. Simple random sampling method (also known as pure random sampling method); 2. Stratified sampling method (also known as the typical sampling method, partition sampling method) ; 3. Group sampling method (or group sampling method); 4. Second-order sampling method; 5. Double sampling method. In each of the above sampling methods, there are two types of samples, one is non-return and the other is non-return. The former is also called non-repeated sampling and the latter is called repeated sampling. As the sampling is randomly selected, and randomly selected methods commonly used indoor lottery or random number table. Fields are common in insects