Sweep samples of tropical deciduous forest foliage-inhabiting insects: seasonal changes and inter-field differences in adult bugs and beetles

Abstract

Sweep samples in four different pasture sites and adjacent deciduous forest understory in Guanacaste Province, Costa Rica produced some tentative conclusions about the structure of the of adult beetles and bugs: a) during the dry season, the different areas in the deciduous forest understory are of widely different value to beetles and bugs; b) the density and species-richness of beetles and bugs is severely reduced by the dry season in all sites except the portions of the forest understory beneath occasional evergreen trees; c) among the four pasture sites in the rain y season, there is nearly as wide a range of numbers of species and individuals as had been found in all the different secondary vegetation sites sampled previously in Costa Rica; d) during the dry season, there appears to be a higher per cent of the beetle species in common between forest understory and pasture sites than in the rainy season; and e) in one of the richest sites swept previously, 312 species of beetles were taken with 800 sweeps, while in the present study, 16,000 sweeps in five habitats and two seasons were required to accumulate 320 beetle species-the figures for adult bugs are generally the reverse, emphasizing that two major orders may display quite different patterns of community structure.