588 THE TROPICAL WORLD. 



whose means of locomotion are domestic animals ; for it is well known that the bite 

 of this poisonous insect is certain death to the ox, horse, and dog. Fortunately it is 

 limited to particular districts, frequently infesting one bank of a river while the other 

 contains not a single specimen, or else traveling in South Africa would be utterly 

 impossible, and we should now know no more of Lake Ngami or the Zambesi than we 

 did thirty years since. In one journey Livingstone lost no less than forty-three fine 

 oxen by the bite of the tsetse. A party of Englishmen once attempted to reach 

 Libebe, but they had only proceeded seven or eight days' journey to the north of the 

 Ni^ami, when both horses and cattle were bitten by the fly, and the party were in 

 consequence compelled to make a hasty retreat. One of the number was thus deprived 

 of as many as thirty-six horses, excellent hunters, and all sustained heavy losses in 

 cattle. 



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 cow. 

 Tlie mule, ass, and goat enjoy likewise the same immunity, and many large tribes on 

 the Zambesi can keep no domestic animals except the latter, in consequence of the 

 scourge existing in their country. Dr. Livingstone's children were frequently bitten, 

 yet suffered no harm ; and he saw around him numbers of zebras, buffaloes, pigs, 

 pallahs and other antelopes, feeding quietly in the very habitat of the tsetse, yet as 

 undisturbed by its bite as oxen are when they first receive the fatal poison, which acts 

 in the following manner: After a few days the eyes and nose begin to run, the coat 

 stares as if the animal were cold, a swelling appears under the jaw, and, though tha 

 animal continues to graze, emaciation commences, accompanied with a peculiar flac- 

 cidity 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 

 wound 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 one may, the poor animals perish miserably, as there is no cure yet 

 known for the disease. 



The Abyssinian Tsalt-salya, or Zimb, described by Bruce, seems identical with the 

 tsetse, or produces at least similar symptoms. At the season when this plague makes 

 its appearance, all the inhabitants along the sea-coast, from Melinde to Cape Gardafui, 

 and to the south of the Red Sea, are obliged to retire with their cattle to the sandy 

 plains to preserve them from destruction. 



The French traveler, D'Escayrac, tells us of a fly in Soudan which leaves the ox 

 uninjured, but destroys the dromedary. On account of this plague the camel is con 

 fined to the northern boundary of the Soudan, while the oxen graze in safety through- 

 out the whole country. This fly has caused more migrations among the Arabs of the 

 Soudan than all their wars; and in the dry season it even drives the elephant from 

 Lake Tsad by flying into its ears. 



Though Locusts not seldom extend their ravages to the steppes of southern Russia, 

 though they have been known to burst like a cloud of desolation over Transylvania 

 and Hungary, and stray stragglers now and then even find their way to f^ngland, yet 

 their chief habitat and birthplace is the torrid zone. They wander forth in countless 



I 



