The number of samples, their sizes and the choice of research methods are based on the level of certainty you want. For that kind of cost-benefit considerations you should let a zoologist help to define the problem and propose solutions to suit the individual cases.
Samples may be taken as samples of packaged goods or averaged samples in accordance with generally accepted principles. Average samples are collected best when a batch is moved. If the products are not being moved the samples can be obtained with a test rod.
Live pests behave differently than other analysis objects and are never spread homogeneously in a product. Often they clump together in the parts of a consignment that is moist, warm or old. If you want to be reasonably certain of getting any pests for the sample, it may be worthwhile to take most tests just there. Mites, booklice and other pests that do not tolerate dry conditions, can be found in the samples from a moist part of the consignment. If one – to get an average sample of the whole lot – mixes tests from wet and dry parts of the products, there is a risk that these pests die because it is too dry in the average sample. This will of course give an inaccurate picture of the state. Live pests may be rushing about. It should be taken into account in both sampling as well as in the communication of the sample. Tightly closed plastic bags are – for at short period of time – sufficient safety against escapes. Check the samples as soon as possible and store them until then at room temperature. It is tempting to store plastic bags with reference samples as evidence of live pests. It should, however, only be done for a short period of time. The samples eventually become so changed that it is no longer representative of the party they were taken from.