Summary
Thirty-six subgenera comprise the biting midge genus Culicoides Latreille, 1809. One of these, the relatively small subgenus <i>Avaritia</i> Fox, 1955, is the most important as it contains nearly half of the 30 world species of Culicoides known to play a greater or lesser role in the transmission of orbiviral diseases to livestock pantropically. These diseases include bluetongue (BT), African horse sickness (AHS) and epizootic haemorrhagic disease of deer (EHD). The subgenus Avaritia is distributed globally and the 70 species described have been subdivided into seven species groups and four subgroups. These 11 informal categories, variously labelled as either ‘subgroups’, ‘groups’ or ‘complexes’, are reduced here to seven in number (six species complexes and one subgroup) and although they appear natural, they are nearly all poorly defined. In this study two of these, namely the Imicola and Orientalis species complexes, are re-evaluated to determine which morphological characters define them more precisely, and so may help to establish their monophyly in the future. The two complexes are separable on eight discrete adult characters (two in the female, six in the male); these characters, and three secondary ones, are discussed and illustrated. The Imicola and Orientalis Complexes together embrace 23 species; these species are assigned to their respective complexes and according to recent nomenclatural adjustments. The taxonomy of vector Culicoides worldwide remains superficial; to improve the situation it is recommended that the ‘traditional’ morphological method be integrated with the ‘modern’ molecular approach.

Keywords
Culicoides, Imicola Complex, Orbivirus vector, Orientalis Complex, Subgenus Avaritia, Taxonomy.