114 INSECTS AND MAN 



destroyed around dwellings ; habitations were screened to 

 keep out mosquitoes, and breeding places that could not 

 be destroyed or drained were treated with crude paraffin, 

 whilst people who neglected to cover their water tubs or 

 allowed water to stand about their dwellings were fined. 

 Over 1,200 men were employed in the work, at an annual 

 cost of $2,000,000 per annum ; in fact, the total expenses 

 of the Panama Canal Sanitary Department have been 

 estimated at a little more than five per cent, of the total 

 cost of the Canal. 



What is the result of this work, taken in hand in 1904 ? 

 Yellow fever is practically unknown ; there was not a single 

 case between 1905 and 1910, and the number of malaria 

 cases has been materially reduced. By the courtesy of the 

 Panama Canal Commission we are enabled to reproduce 

 three photographs illustrative of mosquito control. Plate 

 V. represents the burning of grass near the haunts of the 

 malaria mosquito ; as the adult insect is not strong on the 

 wing, it is partial to places where a luxuriant undergrowth 

 will afford the necessary shelter. Plate I. shows one of 

 the coloured workers of the Sanitary Department treating 

 a ditch a likely mosquito breeding place with crude oil 

 from a knapsack sprayer, in order to kill the larvae. The 

 same end is attained in a different manner by the apparatus 

 shown in Plate VI. A metal container is fixed on supports 

 above some waterway where the mosquitoes abound ; crude 

 oil drops slowly from the container to the water below, 

 thereby rendering the place unsuitable for mosquito breed- 

 ing and killing any larvae that may be present. 



Of Btegomyia fasciata itself, we have already given 

 some details in our account of the malaria mosquito, by 

 way of comparison with that insect. Although what may 

 be termed a coastal mosquito, it readily spreads into the 

 interior of the countries where it is found. Unlike the 

 malaria mosquito, Stegomyia is essentially a town insect ; 

 in fact, it has been called the " cistern mosquito." It has 



