The distribution and species characteristics of the Culicoides biting midge fauna of South Africa

1. Monthly light trap collections over 2 years at 39 sites across South Africa captured over 3 000 000 Culicoides of 86 species, some of them known vectors of African horse sickness and bluetongue viruses. 2. To aid disease control and risk evaluation, cluster analysis and association measurements were carried out on species present at each site. Six species occurred at almost all sites. From the remaining 80 species, eight clusters were identified at > 48% similarity. 3. Culicoides citroneus and C. krameri were characteristic of cluster 8, C. loxodontis of cluster 4, and two numbered, but un-named, species, C. # 119 and C. # 89, of cluster 5. 4. Multiple ANOVA and multiple discriminant analysis on the climatic and geographic parameters of sites in each cluster gave two significant discriminant functions that explained 91.5% of the variance between clusters. Function 1 contrasted sites with high cold cloud duration and high vegetation index with sites with high wind speeds. Function 2 contrasted upland clusters that also had high cold cloud duration with hotter, lower altitude sites. 5. Species associations were explained in terms of biotic provinces, based on ecogeographic factors that have previously been useful to describe communities of birds. 6. None of the clusters was ideal for siting an African horse sickness-vector free quarantine station as C. imicola and C. bolitinos, the main vectors, were found in all clusters but in very low abundance in cluster 5. The analysis provides a firm basis for studying the changing patterns of species distribution under varying climatic influences.