44 INSECTS AND DISEASE 
work has been carefully done the death rate from malaria has been re- 
duced to a small fraction of that formerly prevailing. 
Other Diseases Transmitted 
Yellow fever is transmitted solely by certain species of mosquitoes. 
In Montana and Idaho a disease known as spotted fever is carried 
by a tick. The terribly fatal bubonic plague is transmitted largely by 
fleas. A species of fly has been found to be the means of spread of the 
sleeping sickness that has been ravaging some sections of Africa. Yet 
this is only a part of the known list. 
Among domestic animals, a striking example is found in the disease 
known as Texas fever, which has caused tremendous losses among 
owners of cattle. The organism causing this disease is carried by a 
species of tick, and infection invariably takes place only through the 
bite of this tick. In Asia and Africa other serious or fatal diseases 
of domestic animals have been traced to insect carriers, and it is 
probable that similar discoveries will be made here. 
e 
