Descriptions of the 1st, 2nd and 3rd instar larvae and the puparium of Kirkioestrus minutus are given. First instar larvae, which have not previously been described, can be distinguished from other oestrid larvae by the ventral spinulation of segments IV-XII and the spinulation of the anal protuberance. Of 55 blue wildebeest examined in the Kruger National Park all but two 1-month- old and one 2-month- old animals were infested. First stage larvae are probably deposited in or on the nostrils and may develop within 30 days, initially in the nasal passages and then in the frontal sinuses to mature 3rd stage larvae. Development within the host appears to take longer during the cooler months of the year. Pupal periods vary from approximately 32 days in early or late summer to more than 50 days in winter. Three of 6 blesbok examined at Badplaas in the
eastern Transvaal were infested with 1st instar larvae only of K.minutus and it is suggested that blesbok may not be suitable hosts of this fly. Four black wildebeest in the Golden Gate National Park in the eastern Orange Free State were not infested.