BIVOLTINISM, SURVIVAL RATES AND REPRODUCTIVE CHARACTERISTICS OF THE SCOTTISH BITING MIDGE, CULICOIDES-IMPUNCTATUS (DIPTERA, CERATOPOGONIDAE) IN SCOTLAND

Studies on Culicoides spp. biting midges in south-west Scotland in 1991 revealed that Culicoides impunctatus Goetghebuer, the dominant species throughout the season (May-September), was bivoltine, with a generation period of six weeks. Unseasonal climatic conditions during much of June resulted in a low proportion of first generation females surviving to the parous stage and a reduction in the overall, expected size of the second generation. Distinct behavioural phases of the female midges, such as resting, dispersal and host-seeking, were shown to be directly related to parity states (determined by fat body condition and ovarian development) during the gonotrophic cycle. Female flight activity increased after laying the first, autogenous egg batch, whereas males never flew far from the emergence site. The mean parous rate formula was used to calculate the survival rate of second generation nulliparous females, which was 0.57 per gonotrophic cycle.