The numbers of buffalo flies on individual animals in a herd containing 4 water buffalo, 4 Brahman, 4 Belmont Red (50% Zebu blood) and 3 Hereford Shorthorn steers were counted on 1 I occasions during the 1976/7 wet summer season at Rockhampton, ( 2 3 3 , 150'W). There were consistent differences in the numbers of buffalo flies found on individual animals within a herd. On average there were about 5 times as many flies on the most heavily infested individual as on the least heavily infested. These differences persisted throughout the summer months and at times of high and low fly burdens. The differences were not related to the proportion of Brahman blood of the individual. The numbers of buffalo flies on cattle and water buffalo were similar. In another experiment, during the 1979/80 wet season, the numbers of buffalo flies were counted on 10 occasions on individual animals within separate herds of Brahman, crossbred and 7/8 British cattle maintained in adjacent paddocks. Coat colour did not influence the numbers of buffalo flies on individuals within each herd. The Brahman herd carried about half as many flies as the crossbred herd and about one third as many flies as the British breed herd.
IntroductionBlood-feeding flies locate and choose their preferred hosts by responding to a variety of olfactory, visual and thermal stimuli (Gillies and Wilkes 1969;Vale 1977;Kinzer et al. 1978;Dalton et al. 1978). Most of these flies (e.g. mosquitoes, tsetse, tabanids) leave their host after feeding, but Haematobia irritans (L.) remains in close association with its bovine host during the days prior to oviposition (McLintock and Depner 1954). Two subspecies are recognised, the horn fly Haematobia irritans irritans (L.), and the buffalo fly H. irritans exigua De Meijere, but their biology is very similar (McLintock and Depner 1954; Seddon 1967). Information is available about the host preferences of the horn fly (Marlatt 1910; Bruce 1940; Burns et al. 1962; Franks et al. 1964, Tugwell et al. 1969; Dobson et al. 1970; Christensen and Dobson 1979), but no quantitative data have been published on those of the buffalo fly.There is considerable contradiction in the literature about the host preferences of H . irritans exigua. Krijgsman and Windred in their original paper published in both Dutch and German (1930) report that the buffalo fly found the smell of the hide of buffalo, Zebu and European cattle equally attractive when these odours were presented in cotton wool pads; the smell of the hide of horse and dog was less attractive than that of the bovines. A summary in English of the same data (1933) states that the order of preference of the buffalo fly was Friesian cattle, Zebu cattle, buffalo, horse, but in the previous year Handschin (1932) states that "attractiveness in descending order of preference, is the buffalo, cattle, horse". The issue is further complicated by Du Toit (1938) who stated that Kryjgsman (sic) and Windred have shown that "buffalo exert by far the strongest attraction for the fly; next in order come Z...