PAPERS ON MEDICINE AND PUBLIC HEALTH 2S9 



green and 100 parts of road dust, and strewn with the 

 wind over marshes and swamps, a great reduction in 

 anopheline breeding can be noted. This is explained by 

 the fact that the Anopheles wigglers or larvae, swim- 

 ming on the water surface, come in contact with the 

 arsenic flakes, while the other larvae do not. 



The stocking of ponds and lakes with the top minnow 

 known as Gambusia affinis, is an important means of 

 control, for these little fishes swimming near the surface 

 of the water and near the banks devour the mosquito 

 wigglers. If the fish are present in sufficient numbers, 

 namely, about one minnow for each yard of shore line, 

 and no protection is afforded the wigglers by grass and 

 other growths through which the minnows can not pene- 

 trate they will establish complete control. Kain barrels 

 and other man-maintained mosquito-breeding places in 

 cities can be controlled by rigid house-to-house inspec- 

 tions, by the passing of mosquito ordinances and educa- 

 tional measures. 



For the control work at Carbondale a working map 

 was prepared showing all ditches, streams, lakes, ponds, 

 depressions, and other possible mosquito-breeding places 

 in the area to be controlled. The area comprised all land 

 within the city and one mile in each direction from the 

 city limits. The mosquito-breeding places included about 

 60 acres of cat-tail swamps on the north side, a 40-acre 

 lake on the south side, a number of small ponds and 

 about 6 miles of ditches and streams, all within mosquito- 

 flight distance of the city. The trouble was augmented 

 by an enormous number of rain barrels and open wells 

 and cisterns. 



The control of the natural breeding places was com- 

 paratively easy, and the greatest difficulty was the breed- 

 ing in rain barrels and other man-maintained places. 

 Control was carried on by means of drainage, clearing 

 of existing ditches, oiling, use of top minnows in ponds, 

 open wells and cisterns, and the scattering of Paris green 

 and road dust. The Illinois Central Eailroad constructed 

 by use of dynamite 9,000 feet of ditch for the drainage 

 of the swamps. The first estimate of cost for draining 

 and clearing the swamps was $8,000, of which $2,500 was 



