ORDER XII. DIPTERA.— THE TSETSE FLY. 341 
These insects are of a most ferocious character, and often leave cattle 
which they have attacked covered with blood. Those who keep horses gen- 
erally clothe them in summer with a net as a protection against these per- 
sistent and vexing foes. Even the lion himself flees in terror before an 
African species, which Bruce has described under the name of Tsaltsalyia, 
and Livingstone under the designation of Tsetse Fy. The latter affirms 
that, in traversing a certain region in Africa, he lost forty-three fine oxen 
by the bites of this fly. He remarks, — 
“A most remarkable feature in the bite of the Tsctse is its perfect harm- 
lessness 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 color, as the mandibles come into operaticn. 
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 intervene : 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 temper- 
ature produced by falls of rain seem to hasten the progress of the complaint 5 
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 beneath the 
skin is seen to be injected with air, as if a quantity of soap-bubbles were 
scattered over it, or a dishonest, awkward butcher had been trying to make 
NO. XX. 96 
