ESTIMATING DENSITIES OF GRASSHOPPER (ORTHOPTERA, ACRIDIDAE) ASSEMBLAGES USING BINOMIAL SAMPLING

Counts of grasshoppers from Wyoming and New Mexico were related to the proportion of 0.1-m2 samples that contained grasshoppers through bino mial sampling models. Three models were investigated. One was based on the Poisson probability density function and two were based on the Na chman and logit binomial regressions. The Nachman and logit regression s were tested extensively for an influence of predominant instar, samp ling year, and location on the estimated parameters. Results indicated that instar and sampling year did not influence the parameter estimat es, but location did. All models were then tested to determine which p rovided the smallest error for predicting densities from incidence and vice versa. Results showed that no differences occurred between model s. Based on this finding, the Poisson sampling model was selected for use in wide-scale surveys because it is simple and easy to use. An ind ependent data set from Montana was used to validate this model. Implic ations of this and other findings in context of using binomial samplin g as a management and research tool are discussed.