Notes on Environmental Determinants of Tropical Versus Temperate Insect Size Patterns

The tendency for the lengths of adult insects of sweep samples from forest understories, considered both as species and as individuals, to fit a two-parameter lognormal distribution rather than a simple normal distribution, and a three-parameter lognormal distribution best of all, is documented for some tropical and temperate areas. Two features of the habitat, the variation of moisture patterns in space and the fluctuation of resources in time, appear to be correlated with most of the differences in the means and standard deviations of these distributions. In general, samples from drier areas or those with longer growing seasons have larger species, and samples from areas with the more uniform moisture conditions and growing seasons have the smaller standard deviations of their species' lengths.