306 ENTOMOLOGY 
remain in the thoracic muscles for a time and become larvze, 
which at length pass through the proboscis of the mosquito 
into the skin, of man. It is possible, though not proved, that 
other mosquitoes than Culex and indeed other kinds of insects 
are involved in the transmission of filariasis. 
In Egypt, an eye disease is transmitted by the house fly. 
There is some evidence that the bubonic plague is spread 
through the agency of fleas. Anthrax of cattle is carried by 
gad flies (Tabanide). A South African disease fatal to 
horses, cattle and dogs, though not to man, is transmitted 
from infected to healthy animals by the proboscis of a muscid 
fly, Glossina morsitans, as has been mentioned. The specific 
cause of this disease is a blood parasite similar to that of 
malaria. Finally, the destructive Texas fever of cattle is 
undoubtedly transmitted by the common cattle-tick, as was 
discovered by Theobald Smith, though the tick 1s not, properly 
speaking, an insect. 
