OVERWINTERING OF CULICOIDES SPP (DIPTERA, CERATOPOGONIDAE) IN THE HUNTER VALLEY, NEW-SOUTH-WALES

In a study of the overwintering ability of Culicoides spp, at the sout hern limits of the distribution of Culicoides brevitarsis Kieffer, it was found that C. brevitarsis numbers declined linearly with temperatu re during winter but were independent of rainfall. Regression equation s were used to calculate lower thresholds for C. brevilarsis activity/ presence. These thresholds were similar for three different collection methods. Results obtained from light trap data for four other Culicoi des spp showed that their relationship with temperature allowed their recovery after winter. Under suitable conditions, oviposition by C. br evitarsis continued into winter and immature stages survived for 1 to 2 months (mainly as pupae/pre-pupae) in cattle dung, its breeding habi tat. Survival of C. brevitarsis was affected by the time spent at temp eratures below the estimated thresholds. Reinfestations from coastal r egions further north could be responsible for the reappearance of C. b revitarsis in years when they fail to survive in the central coastal r egion of NSW . Conversely, the other Culicoides spp. recorded appeared capable of maintaining viable populations.