The effect of the activity of the African dung beetle Catharsius tricornutus De Geer (Coleoptera: Scarabaeidae) on the survival and size of the African buffalo fly, Haematobia thirouxi potans (Bezzi) (Diptera: Muscidae), in bovine dung in the laboratory

Abstract

AbstractThe effect of dung burial by the African dung beetle Catharsius tricornutus De Geer on the survival and size of the dung-breeding African fly Haematobia thirouxi potans (Bezzi) was examined in the laboratory at 25°C using 1-litre pads of cattle dung. The experiment included a set of dung pads which were exposed to infrared radiation for 12 h per day to mimic the heating effect of solar radiation. C. tricornutus is a large (1–2-g live weight) dung beetle, and moderate numbers can completely bury dung pads within 24 h of pad colonization. Dung burial was proportional to the number of pairs present (range 0–8 pairs per pad), but the level of burial was reduced in the presence of infrared radiation. Dung pads lost moisture with time, and the rate of desiccation of unburied dung increased with the amount of dung burial and under infrared radiation. Mortality in the immature stages of H. t. potans increased with increasing levels of dung burial and with exposure of pads to infrared radiation. The timing of addition of dung beetles (i.e. before or after egg hatch) did not affect fly survival. At moderate levels of dung burial, fly larvae were killed directly by beetle activity and at high levels of dung burial, fly larvae also perished due to an unfavourable physical environment associated primarily with moisture stress. Infrared radiation killed immature flies and increased the level of moisture stress. There was a low level of survival in dung buried by the beetles under these unnatural laboratory conditions. Stunting of surviving flies was associated with reduced levels of moisture in the core of the unburied dung and was observed when the level of dung burial was >60% in ambient conditions and >40% under infrared radiation.