Differential emergence of Culicoides (Diptera: Ceratopogonidae) from on-farm breeding substrates in Northern Ireland.

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are vectors of a number of viral diseases worldwide. Following the unforeseen outbreak of bluetongue in northern Europe (2006–2009) there was a need to clarify on-farm breeding substrates utilized by temperate Culicoides spp. Six substrates (cow dung, cow slurry, horse dung, sheep dung, maize silage and soil) were investigated for Culicoides spp. emergence over a 31-week period. Overall, most Obsoletus group Culicoides emerged from the cow dung and the most Pulicaris group Culicoides emerged from the sheep dung. Furthermore, Culicoides of the Obsoletus group were found to be abundant in cow slurry and sheep dung. Temperature played a significant role in the emergence times of adult Culicoides. The Obsoletus group appear to have undergone 3 generations during the experimental period. The sex ratio of emergent Obsoletus group Culicoides was affected by substrate type, with a greater proportion of males emerging from cow dung and slurry compared with the other substrates.