Number of Adult Culicoides Brevitarsis Kieffer (Diptera: Ceratopogonidae) Emerging From Bovine Dung Exposed Under Different Conditions in the Field.

Abstract

Numbers were recorded of adult C. brevitarsis emerging from standard samples from variously treated dung pats. Adult emergence was a more efficient technique than the extraction of immatures. Emergence increased linearly by from three to four ovipositions per pat per day over the first 7 days of exposure of pats in the field. Oviposition occurred throughout the diel, maximum 1400-1800 h and minimum 0000-0700 h. Emergence began 11 days after pats were exposed and was completed by day 24. From days 12 to 24 numbers emerging halved every 1.7 days. Eggs were deposited all over the upper surface of pats with greatest density at the centre. Number emerging per unit area was independent of pat size. Adults emerged from pats of varying shape in plan view but few from pats sunk flush with the ground, surrounded by a sleeve, or subjected to heavy rain within 24 h of deposition. It is suggested that emergence rates reflect oviposition rates, and it is concluded that C. brevitarsis orients visually to dung, probably while flying above it. The rounded sides of the pats may be very important.