POSSIBILITIES AND COSTS. G5 



its deadly nature when applied to the Culieidse; (3) its com- 

 paratively harmless nature as apjilied to other forms of aquat- 

 ic life ; and (4) the ease with wliich it can be applied. 



Of the first claim we only care to say that three dollars' 

 worth of the crude oil will suffice, according to our esti- 

 mate, to cover an area of one hundred acres of water surface 

 five times in one season. In this way every brood would 

 be greatly retarded or entirely destroyed in that area. In 

 illustration of the second claim we may state that mosquito 

 larvae lived as long in pure Brown's Jamaica Ginger as 

 they did in water covered with a film of oil. The depth 

 of the water does not signify. Culex must come to the 

 surface to breathe. If the oil is sprayed, as illustrated in 

 Plate VII., Fig. 2, it need not interfere with the herbage. 

 Odonat larvffi will not be found in stagnant water, and fish 

 must have fresh water, but oil may be carefully sprayed 

 over any surface however small. The tube may be at- 

 tached to a fishing pole in order that a spray may be 

 thrown some distance. A Riley or Cyclone nozzle is best 

 adapted to this purpose. In closing this account of Cu- 

 licicides it is well to call attention to a paper by Dogiel,^^ 

 in which a description of the eifect of twenty-two poisons 

 on Culex are given. 



The possibilities for destroying members of the IMus- 

 cidse are not so promising as are those of the Culicidae, 

 owing to their hidden habits and the repulsive nature of 

 their breeding places. 



Under the discussion of general insecticides at the be- 

 ginning of this chapter, the treatment of pyrethrum, gases, 

 certain parasites, yeast, and other fungi have special bear- 

 ing on the fly problem. 



As it appears to us, the only very promising methods 

 are cultivation of fly fungus and the oil treatment. 



