Sampling plans for beneficial arthropods in cereals.

Abstract

In 1977, 1980, 1984 and 1985 different sampling techniques, pitfall trapping, quadrat counts and suction sampling, were used to obtain information on the spatial distribution of Carabidae and Araneae in cereals. Means and variances were calculated for the different samples and the extent to which Taylor 's Power Law applied to the different species investigated. The index of aggregation, b, varied from 1.09 to 1.36 and from 0.98 to 1.45 for the different species of Carabidae and Araneae respectively. For a given species, b was similar for different sampling methods and in different years . The number of sample units required to obtain population  estimates with a standard error of 20% of the mean was calculated for different mean numbers of Carabidae and Araneae . The number required for the different species varied from 17 to 42 and from 5 to 14 when the mean number per sample unit was 1.0 and 5.0 respectively.