Effect of Time of Day on Efficacy of Sweep Net Sampling of Arthropod Predators in Maize Agro-Ecosystems in the North West Province, South Africa

Abstract

Various abiotic factors influence the biology and behaviour of arthropods, one of the most prominent abiotic factors is temperature. Thus, it is essential to know the optimal time of day during which sampling of target species should be done to allow for accurate arthropod biodiversity studies. This study considered species richness, abundance and diversity of predaceous arthropods of the Chrysopidae, Mantodea, Araneae and Coccinellidae throughout the day in and around maize fields in the extensively cultivated highveld grasslands of South Africa. Sweep net sampling was done at the following times: 07:00, 12:00, 15:00 and 17:00. Sampling was conducted at three different localities and repeated on three occasions over two growing seasons. At each locality there were three replicates in each of three zones in the agro-ecosystem, i.e. maize field, field margin and untransformed grassland. Shannon diversity index values did not differ significantly between the different sweep net sampling times. Predacious arthropods were, although not significantly so, more abundant within maize fields in the mornings (07:00) and in adjacent grasslands during late afternoon (15:00). This study indicated no particular time to be significantly better suited for sampling of the diversity of the four groups of predacious arthropods in maize agro-ecosystems.