74 THE INSECT WORLD. 
Livingstone, the celebrated traveller, in crossing those regions 
of Africa that are watered by the Zambesi, lost forty-three mag- 
nificent oxen by the bites of the Tsetse fly, notwithstanding that 
they were carefully watched, and had been very little bitten. 
“A most remarkable feature in the bite of the Tsetse is its 
perfect harmlessness in man and wild animals, and even calves 
so long as they continue to suck the cows. We never experienced 
the slightest injury from them ourselves, personally, although we 
lived two months in their habitat, which was in this case as sharply 
defined as in many others, for the south bank of the Chobe was 
infested by them, and the northern bank, where our cattle were 
placed, only fifty yards distant, contained not a single specimen. 
This was the more remarkable, as we often saw natives carrying 
over raw meat to the opposite bank with many Tsetses settled on it. 
“The poison does not seem to be injected by a sting, or by ova 
_ placed beneath the skin, for, when one is allowed to feed freely on 
the hand, it is seen to insert the middle prong of three portions, 
into which the proboscis divides, somewhat deeply, into the true 
skin. It then draws it 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, but 
not more than in the bite of a mosquito. In the ox this same 
bite produces no more immediate effects than in man. It does not 
startle him as the gad-fly does; but a few days afterwards the 
following symptoms supervene: the eye and nose begin to run, 
the coat stares as if the animal were cold, a swelling appears uhder 
the jaw, and sometimes at the navel; and, though the animal 
continues to graze, emaciation commences, accompanied with a 
pecular flaccidity of the muscles, and this proceeds unchecked 
until, perhaps months afterwards, purging comes on, and the 
animal, no longer able to graze, perishes in a state of extreme 
exhaustion. Those which are in good condition often perish, soon 
after the bite is inflicted, with staggering and blindness, as if the 
brain were affected by it. Sudden changes of temperature pro- 
duced by falls of rain seem to hasten the progress of the complaint ; 
but in general the emaciation goes on uninterruptedly for months, 
and, do what we will, the poor animals perish miserably. 
