74 THE INSECT WORLD. 



Livingstone, the celebrated traveller, in crossing those regions of 

 Africa that are watered by the Zambesi, lost forty- three magnificent 

 oxen by the bites of the Tsetse fly, 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 Tsetse 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 under 

 the jaw, and sometimes at the navel; and, though the animal 

 continues to graze, emaciation commences, accompanied with a 

 peculiar 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 produced 

 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. 



" When opened, the cellular tissue on the surface of the body 



