POSITIONS OF JUVENILE STAGES OF CULICOIDES-BREVITARSIS KIEFFER (DIPTERA, CERATOPOGONIDAE) AND OF 4 OTHER FLIES IN BOVINE DUNG

A study was made of the positions of juvenile stages of Culicoides bre vitarisis and of four other species of flies (Diptera) breeding in bov ine dung. The objective was to provide information on sampling cores o f dung for laboratory experiments and to study fly behaviour associate d with the breeding habitat. Oviposition and field exposure of dung we re restricted to 2 d and this enabled relatively discrete populations of flies to be investigated. All species were reasonably abundant afte r 2 d of oviposition. Distributions were contrasted by dividing the du ng into vertical and horizontal segments. C. brevitarsis, Australoseps is niveipennis and Leptocera mirabilis oviposited mainly in the top of the dung, while Sepsis nitens and Psychoda sp. oviposited mainly in t he lower half. After hatching, the proportions of flies varied between positions and over time. Except for C. brevitarsis, the adult flies w ere reared from the half of the pat associated with oviposition. C. br evitarsis and A. niveipennis rearings were evenly distributed in centr e and outer positions 4 d after dung deposition and C. brevitarsis sho wed clear changes in vertical position over lime. Moisture content in the dung decreased by 16.1% after 10 d, mainly in the upper half of th e pat. Greater numbers of C. brevitarsis were associated with areas of higher moisture. The fly species varied in their times of emergence w ith C. brevitarsis emerging later in the lower half positions than in the upper half positions 10 d after deposition of the dung. A procedur e for sampling cores of dung is proposed.