In Dhofar, pastoralists take certain precautionary measures against hematophagous flies: Haematobia minuta Bezzi, Musca crassirostris Stein and Forcipomyia (lasiohelea) whitcombei Boorman. Through their feeding on domesticated animals, these flies impede pasturing in certain areas during the rainy season (Khareef); hence they act as a limiting ecological factor and a custodian of the flora. The possibility that these flies could be potential pathogenic vectors has not been investigated in Oman, although in other parts of the world they are recognized as carriers of disease agents. The paper draws attention to this issue in Dhofar.