Diversity, abundance and behaviour of diurnal insects on flowering capitula of commercial sunflower in the Transvaal

Abstract

Sunflower, Helianthus annuus L., is an insect-pollinated crop and the different insect taxa visiting the flowering head play a role of greater or lesser importance in cross-pollination. Species diversity, abundance and behaviour of insects visiting commercial sunflower during flowering are reported for three sites in the Transvaal during 1985–87. The conventional strip-counting method was used to determine diversity and abundance, while notes on behaviour were taken at the same time. The mean number of insects per 100 capitula was 45, 147 and 64 at Settlers, Pretoria and Hartbeesfontein, respectively. Indigenous honeybees, Apis mellifera saltellata Lepeletier, were the most common in all study areas (71%, 86% and 46%, respectively). Other well-represented taxa included Heliothis armigera Hübner (American bollworm larvae), Asiylus atro- maculatus Blanchard (spotted maize beetles), Diptera (flies) and Hemiptera (bugs). Solitary bees were rare.