The effect of light trap height on the numbers of Culicoides midges collected under field conditions in South Africa.

Onderstepoort 220 V suction light traps were operated at four sites at the ARC-Onderstepoort Veterinary Institute to collect Culicoides midges (Diptera; Ceratopogonidae) at 0.6, 1.4, 2.2 and 2.8 m above ground level. Trap heights at these four sites were alternated in three replicates of a 4 x 4 randomized Latin square design. Culicoides midges belonging to 20 species were collected in 48 collections made from 15 to 30 September 2008. The two most abundant Culicoides species to be collected were Culicoides imicola Kieffer (94.2-95.85%) and Culicoides magnus Colaço (2.21-2.72%). Most Culicoides midges were collected at a height of 2.8 m (44.8% of 147158). Statistically significant differences in light trap results were found in the number of midges collected, species composition, parous rates, sex ratios and insect to Culicoides ratios at the various heights. Light trap height is one of a variety of factors that may influence light trap results and highlighted the problems involved in the reliable comparison of light trap data between collection sites. This study emphasized the need for the standardization of techniques for measuring the variables of vectorial capacity.