In the cool of the mornings and evenings it is less agile. Its peculiar buzz when once heard can never be forgotten by the traveller whose means of locomotion are domestic animals, for its bite is death to the ox, horse, and dog. In one of Dr. Livingstone’s journeys, though the traveller watched the animals carefully and believed that not a score of flies were ever upon them, they destroyed forty-three fine oxen. A most remarkable feature is the perfect harmlessness of their bite in man and wild animals, and even calves, so long as they continue to suck the cows, though it is no protection to the dog to feed him on milk. The poison does not seem to be injected by a sting, or by ova placed beneath the skin, for when the insect is allowed to feed freely on the hand it inserts the middle prong of the three portions into which the proboscis is divided somewhat deeply into the true skin. It then draws the prong out a little way and it assumes a crimson colour as the mandibles come into brisk operation. The previously shrunken belly swells out, and if left undisturbed the fly quietly departs when it is full. A slight itching irritation follows the bite. In the ox the immediate effects are no greater than in man, but a few days afterwards the eye and nose begin to run, and a swelling appears under the jaw and sometimes at the navel, and although the poor creature continues to graze, emaciation commences accompanied with a peculiar flaccidity of the muscles. This proceeds unchecked until perhaps months afterwards, purging comes on, and the victim dies in a state of extreme exhaustion. The animals which are in good condition often perish soon after the bite is inflicted, with staggering and blindness as if the brain were affected. Sudden changes of temperature produced by falls of rain seem to hasten the progress of the complaint, but in general the wasting goes on for months. When the carcase is opened the cellular tissue beneath the skin is found injected with air, as if a quantity of soap bubbles were scattered over it. The blood is small in quantity, and scarcely stains the hands in dissection. The fat is of a greenish yellow colour and of an oily consistence. All the muscles are flabby and the heart is often so soft that the fingers may be made to meet through it. The lungs and liver partake of the disease. The stomach and bowels are pale and empty, and the gall bladder is distended with bile. These symptoms seem to indicate poison in the blood, the germ of which enters when the proboscis is inserted.