238 INSECTS AND DISEASE 



ing sickness, a terribly fatal disease afflicting whites and 

 blacks alike in certain districts of tropical Africa. The 

 first symptoms of an attack are often relatively slight 

 fever and skin disorders, but gradually these become 

 more pronounced, and after months or even years the 

 nervous system is affected^ the victim lapsing into a 

 state of unconsciousness from which there rarely is a 

 recovery. After an immense amount of labor it has been 

 determined that this scourge is due to minute, slender 

 and actively moving blood parasites which are carried 

 from man to man by the skin-piercing blood-sucking 

 tse-tse fly. This insect is a dull brown faintly banded 

 species bearing a general resemblance to the ordinary 

 house fly. It makes its home in thickets along the 

 borders of streams and marshy districts, and, as is 

 to be expected, sleeping sickness is confined to these 

 same moist " fly belts. " Other forms of this disease are 

 known to attack cattle, horses, mules and camels in the 

 Eastern Hemisphere, while a related affliction is common 

 among horses in Central and South America. It has 

 been demonstrated that while it is not possible to cut 

 down all the brush in an infested district, the region may 

 nevertheless be made comparatively safe by removing 

 the thickets from the neighborhood of water bodies, 

 bridges and fords. 



Flies and Other Diseases. — The reputation of the 

 house fly, or the typhoid fly as some scientists have sug- 

 gested it should be called, is further blackened by the 

 fact that it may also be the agent responsible for spread- 

 ing several other disorders aff'ecting man. It is certainly 

 known that these insects may fly at least ten miles from 

 their birthplace, and may carry any one of not less than 

 sixty diff'erent kinds of organism attached to their bodies, 

 among which are the germs of diphtheria, infantile par- 

 alysis, measles, leprosy, tuberculosis, Asiatic cholera, 

 scarlet fever and several other important diseases. 

 House flies are also known to carry the eggs of several 



