Colonisation and dispersal studies of the Scottish biting midge, Culicoides impunctatus Goetghebuer
This study investigates aspects of the biology of Culicoides 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 egg-batch over time. Conditions for storage of adults during this period are recommended as 23±4°C/95-100% relative humidity and 16:8 light:dark photoperiod. Oviposition in C. impunctatus is investigated through choice and no-choice bioassays which show Sphagnum spp. mosses to be highly effective in this regard. Juncus articulatus/acutiflorus 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 media for colonisation purposes. The possibility of future colonisation is discussed with reference to both these 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.