Colonisation and dispersal studies of the Scottish biting midge, Culicoides impunctatus Goetghebuer

• Main Author: Carpenter, Simon
• Published: University of Aberdeen 2001
• Subjects: 590; Ceratopogonidae
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368901

This study investigates aspects of the biology of C. impunctatus with a view to producing an optimised laboratory culture of this species. Artificial membrane feeding of C. impunctatus is shown to be enhanced by the addition of blood vestiges to the outer surface of the feeding apparatus. The effects of holding temperature, environment and conspecific density upon oogenesis in blood fed female midges are assessed through mortality, digestion of the blood meal and development of the eggbatch over time. Oviposition in C. impunctatus is investigated through choice and nochoice bioassays which show Sphagnum spp. Mosses to be highly effective in this regard. Juncus articulatuslacutiflorus infusions also significantly increase the number of eggs laid by females in comparison to oviposition substrates used in colonisation of other midge species. Preliminary studies are also carried out to provide a suitable larval medium for colonisation purposes. The possibility of future colonisation is discussed with reference both to those experiments carried out, and to those areas not yet addressed in the C. impunctatus lifecycle. Dispersal of C. impunctatus is also examined, both on a local scale and in terms of gene flow between UK populations. Capture, mark, recapture studies showed the marked population of C. impunctatus remained relatively close to the release site in the habitat used for the study. The effect of prevailing winds, however, was found to be highly important in terms of passive directional movements of individuals. Daily survival rates of parous females were calculated as very low in relation to other species of midge making this species an unlikely candidate for pathogen transfer in Scotland. Polymorphism in the molecular markers used to examine gene flow in C. impunctatus across the UK was minimal and precluded phylogenetic analysis. This result is interpreted in terms of both possible long-distance dispersal and the effects of rapid post-glacial popUlation expansion into the UK.