The Effects of Habitat on the Distribution of Culicoides Brevitarsis Kieffer (Diptera, Ceratopogonidae) During Its Resting Phase

Abstract

Culicoides brevitarsis is a biting midge and a vector of several arboviruses affecting livestock in Australia. The effect of habitat on adults during their resting phase in pasture was studied in the Hunter Valley during 1994 and 1995. C. brevitarsis was 21 times more abundant in grass tussocks (Pea sp.) than in pasture grass and its numbers were related positively to the increasing size of these tussocks. High numbers were also found in reed tussocks (Juncus sp.) and grass along the margins of dams. When tussocks were absent in pasture, numbers of C. brevitarsis varied within the pasture grass during the day. More C. brevitarsis 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 present. Counts in tussocks and grass were lowest and counts in the the air above tussocks were highest 1 h before sunset. After sunset, numbers increased on pasture grass more than in reed tussocks. Numbers in reed tussocks were again high after the morning flight peak the next day. Relationships with weather variables were weak.