Medical and Veterinary Entomology (2013) 27, 441–449 doi: 10.1111/mve.12006 Larval development and emergence sites of farm-associated Culicoides in the United Kingdom L. E. H A R R U P 1,2 , B. V. P U R S E 3 , N. G O L D I N G 1 , P. S. M E L L O R 1 and S. C A R P E N T E R 1 1 Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, U.K., 2 Department of Zoology, University of Oxford, Oxford, U.K and 3 NERC Centre for Ecology and Hydrology, Edinburgh, U.K. Abstract. Culicoides biting midges (Diptera: Ceratopogonidae) are the biological vectors of internationally important arboviruses of livestock including bluetongue virus (BTV). Information on the habitats used by Culicoides for larval development is valuable for establishing targeted vector control strategies and for improving local scale models of vector abundance. This study combines emergence trap collections of adult Culicoides identified using molecular markers and physiochemical measurements of habitats to investigate larval development sites of Palaearctic Culicoides in South East England. The known range of larval habitats for several Culicoides species is extended and the potential BTV vector species C. obsoletus and C. scoticus are confirmed to co-occur in many larval habitats. The presence of emerging C. obsoletus was favoured by increasing substrate moisture level [odds ratio (OR) 6.94 (2.30; 20.90)] and substrate pH [OR 4.80 (1.66; 13.90)] [bias-corrected D xy : 0.68; area under the curve (AUC): 0.86] rather than any particular larval habitat type, as expected for a species with relatively wide larval habitat preference. Of the newly emerged sub- genus Avaritia individuals collected, 23% were observed to have a degree of abdominal pigmentation commonly inferred to indicate parity. If consistent across species and locations, this observation represents a potential source of error for age structure analyses of Culicoides populations. Key words. Culicoides , Avaritia, bluetongue virus, breeding habitat, larval development, parity, pigmentation, vectors. Introduction Culicoides biting midges are the biological vectors of a range of internationally important arboviruses of livestock, including bluetongue virus (BTV) and African horse sickness virus (AHSV) (Mellor et al., 2000). The recent emergence of BTV in northern Europe (Carpenter et al., 2009b), has led to renewed efforts to characterize the larval habitats of Culicoides in this region, with emphasis placed upon defining habitats utilized by those species that have been most strongly implicated in BTV transmission. These include members of the subgenus Avaritia in the UK: Culicoides obsoletus Meigen, Culicoides scoticus Downes & Kettle, Culicoides dewulfi Goetghebuer Correspondence: Lara Harrup, Vector-borne Viral Diseases Programme, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K. Tel.: +01483 232441; Fax: +01483 232448; E-mail: lara.harrup@iah.ac.uk and Culicoides chiopterus Meigen, Culicoides pulicaris L. and Culicoides punctatus Meigen (Carpenter et al., 2006, 2008a; Hoffmann et al., 2009). While most Culicoides species are semi-aquatic as larvae, their habitats are largely poorly defined and the vast majority of species are recognized from adult forms only (Meiswinkel et al., 2004). The UK fauna is unusual, however, in having been described in detail as part of early studies to assess the likely impact of insecticidal control techniques (Kettle & Lawson, 1952). Though the reliability of the morphological speciation may be questionable, these studies identified C. pseudochiopterus (= C. dewulfi ) and C. chiopterus as developing in cattle dung and these species have not since © 2013 The Royal Entomological Society 441