THE EFFECTS OF HABITAT ON THE DISTRIBUTION OF CULICOIDES BREVITARSIS KIEFFER (DIPTERA, CERATOPOGONIDAE) DURING ITS RESTING PHASE

Culicoides brevitarsis is a biting midge and a vector of several arbov iruses affecting livestock in Australia. The effect of habitat on adul ts during their resting phase in pasture was studied in the Hunter Val ley during 1994 and 1995. C. brevitarsis was 21 times more abundant in grass tussocks (Pea sp.) than in pasture grass and its numbers were r elated positively to the increasing size of these tussocks. High numbe rs were also found in reed tussocks (Juncus sp.) and grass along the m argins of dams. When tussocks were absent in pasture, numbers of C. br evitarsis varied within the pasture grass during the day. More C. brev itarsis were found in grass when no cattle were present. The presence of cattle affected the parous ratio, with 85% of females being parous when cattle were absent and only 38% being parous when cattle were pre sent. Counts in tussocks and grass were lowest and counts in the the a ir above tussocks were highest 1 h before sunset. After sunset, number s increased on pasture grass more than in reed tussocks. Numbers in re ed tussocks were again high after the morning flight peak the next day . Relationships with weather variables were weak.