A Simple Apparatus for Measuring Density of Insect Population1

Abstract

Measuring population density is often difficult in field studies of insects. Direct counts of individuals per unit area are possible only with slow-moving species. The sweep net, in wide use for sampling the more active forms, gives only an estimate of relative numbers. A conversion factor, derived from some direct method of sampling, must be used for expressing sweep data in terms of absolute numbers (Beall 1935; Gray and Treloar 1933; and Romney 1945). For sampling the entire aboveground insect fauna the suction-type apparatus of Dietrick et al. (1959) possesses the most general applicability for different vegetational types and species. The suction apparatus, however, is expensive and an extensive laboratory setup is needed for separation of the material collected, if an investigator is interested only in one or a few species of the insect fauna, it is sometimes possible to utilize a faster and less expensive sampling procedure designed specifically for a restricted group of species, such as that described in this note.