HEALTH AND DISEASE 339 



no grounds remained for doubting that one of the greatest detective stories 

 of all times had been brought to a successful close. Sentence was passed 

 on the A'edes aegypti mosquito in these words of Walter Reed: "The spread 

 of yellow fever can be most effectually controlled by measures directed 

 to the destruction of mosquitoes and the protection of the sick against 

 these insects." 



EXECUTING THE SENTENCE IN HAVANA 



W. C. Gorgas, then a Major in the medical corps, United States Army 

 and Chief Sanitary Officer of Havana, set the example for vigorous and 

 energetic measures against the mosquito. 



The female mosquito lays her eggs in still water. About 36 hours later 

 these eggs hatch into larvae, also called "wigglers" or "wiggle-tails." The 

 wiggler moves about actively, feeds much of the time, and breathes air 

 which it secures by thrusting its breathing tube up through the surface of 

 the water. After six or seven days it changes into a pupa or "tumbler." In 

 this stage it is an air-breather but it does not feed, and after 36 hours or 

 more it is again changed and comes forth as the perfect winged insect. 



When the campaign started in February 1901, all houses and yards in 

 Havana were examined and all tin cans, empty bottles, and similar trash, 

 which were generally found filled with rain water and full of yellow fever 

 mosquito wigglers, were carted off. Openings in cisterns were covered 

 with mosquito netting. The Health Department fitted covers over rain- 

 water barrels, and a wooden spigot was placed in the lower part of the 

 barrel so that water could be drawn off without lifting the cover. As the 

 Aeds aegypti mosquito lives and breeds almost entirely in or near houses, 

 these measures were very effective. 



When a yellow fever case was reported, employees of the Health De- 

 partment went to the house and screened it so that no mosquitoes could get 

 out or in. Then they fumigated the house to kill the mosquitoes inside. 



As a result of this general mosquito hunt yellow fever decreased rapidly, 

 and since September 1901 not a single case has developed in the city. That 

 historic month was the first in which Havana had been free of yellow fever 

 in 150 years. Later, Gorgas repeated this performance in the Canal Zone, 

 with the result that the United States was able to build the Panama Canal. 

 Since then the example of General Gorgas has been followed wherever 

 the A'edes aegypti had a hiding place. 



The mosquitoes that frequent the United States and Canada now prob- 

 ably belong to the harmless tribes of that innumerable race. But it is well 

 to remember that all mosquitoes are a great pest, and that the Anopheles 

 mosquito is still spreading malaria. For the sake of comfort and of health 

 everyone should make war on them just as General Gorgas did. 



