SPATIAL DISTRIBUTIONS OF DEFOLIATING
LEPIDOPTEROUS LARVAE ON PEANUTS Introduction
Spatial distributions are a useful means of quantifying the dispersion of insects in a given habitat. Spatial distributions are useful in several ways: (1) to aid in determining the appropriate transformation for analysis of variance; (2) to develop sequential decision plans; and
(3) to develop sampling plans. Also, inferences about the biology of the insect e.g., dispersal patterns, can be made. Spatial distribution models are probability distributions that relate the frequency of occurrence of an event, depending on the mean of the measurements and in some cases on one or more parameters.
The most useful statistical distributions in entomological research have been the Poisson and negative binomial (Southwood 1978). The Poisson distribution describes a random distribution with variance equal to the mean. Most commonly in insect sampling the variance will be larger than the mean, indicating that the distribut i on is aggregated or clumped. The most useful distribution describing a clumped insect population has been the negative bionomial.
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