56 AGRICULTURAL EXPERIMENT STATION. 



winter, a population of hibernating mosquitoes. These hiber- 

 nates, and especially the house mosquito, Ciilex pipiens, breed 

 in so great a variety of places that it is of the utmost importance 

 to check them at every point. Permanent eradication of all 

 breeding places is impossible as against a species that will breed 

 in every sewer catch-basin, in every settling basin in the park 

 drains and in every cess-pool, manure pit or cistern which is in 

 any way open to the air. These things are necessities in modern 

 cities and the sewer catch-basins as at present constructed are 

 open invitations for breeders. This, chiefly, makes the destruc- 

 tion of the hibernates of importance, for all of them are impreg- 

 nated females and all of them are potential progeni'tors of 

 between 400 and 500 specimens. Of course not ten per cent, of 

 those that get into the cellars in fall live through the winter ; but 

 every additional per cent, destroyed by artificial means is a 

 positive lessening of the supply that will be felt throughout the 

 ensuing summer. As the ordinary winter population of a city 

 cellar is rarely less than 100 and often reaches 1,000 the chance 

 for effective work is obvious. Mr. Keller's report which follows 

 will give interesting information concerning the favoring- factors. 

 So far as the discussion of remedies goes, this chapter in part 

 anticipates another section of the Report; but as the subject 

 really stands by itself it is deemed best to present it here as a 

 whole. 



We have, of course, absolutely effective agents for destroying 

 the hibernating specimens ; but all of them are open to some 

 serious objection. The hydrocyanic acid gas formula is as fol- 

 low s : 



For every 100 cubic feet of space use — 



Cyanide of Potassium, 98 per cent, pure, i ounce. 



Sulphuric acid, best commercial, 2 ounces. 



Water, 4 ounces. 



Add the acid slowly to the water in an earthen dish or jar 

 and then drop in the cyanide in a paper bag. The paper retards 

 the formation of gas slightly and enables the operator to get out. 

 This gas, formed by the action of the diluted acid upon the 

 cyanide, is deadly to all animal life and that fact forms the 

 greatest objection to its use. In dwelling houses it is cut out 

 altogether and where it is to be used in public buildings, factories 

 or churches, the cellars should first be made as tight as possible 

 and after the fumigation is started the building should be left 

 closed for at least twenty-four hours before it is entered. Ar- 

 rangements should also be made for opening up the fumigated 



