INSECTS AND DISEASE 



223 



both externally on its feet and body and internally by way of its 

 food and excreta. 



Our common flies transmit typhoid, cholera, summer complaint, 

 dysentery, tuberculosis, and probably other diseases where the 

 germs pass from the body in any form of excrement, pus, or sputum. 

 The tsetse fly of Africa transmits the deadly " sleeping sickness." 

 Thus it is seen that flies which we formerly regarded as an un- 



FIG. 75. Foot of housefly showing claws, hairs, pulvillae and the minute 

 clinging hairs on the pulvillae. From Kellogg and Doane. 



avoidable nuisance, have been proven to be responsible for the 

 death of more people than all wild beasts and reptiles together, 

 and that actually they are more dangerous to man than the tiger, 

 grizzly, or rattlesnake. 



Rate of Reproduction. In the face of its enormous rate of in- 

 crease, " swatting " of individual flies is a losing battle as the 

 following figures show. Supposing that reproduction was un- 

 checked and that all offspring survive (which fortunately is not 



