138 



places as possible for a definite period of time catching" as many 

 specimens as possible. 



In this way the bulk of this brood was traced to the Hacken- 

 sack Valley salt marsh, where the pupal shells were found in 

 the rapidly disappearing- pools on territory formerly reported 

 as free from breeding. By studies of this type, carried out by 

 the chief inspectors of Hudson and Union Counties, by the 

 president and chief inspector of Essex County, and by the 

 writer by himself and in cooperation with above officials, the 

 source of the various broods of A. cantator and A. sollicitans 

 have been discovered, inefficiencies in the drainage systems 

 on the marshes of Union, Essex and Hudson Counties demon- 

 strated and the real character of the Bergen County salt marsh 

 as a prolific breeder of A. cantator established. On the basis 

 of these investigations drainage systems of the three first-men 

 tioned counties have been modified and extended and the drain- 

 age of the last well begun. Hardly had the distribution of the 

 salt-marsh species begun to give positive results, when through 

 a prevalence of C. pipiem in South Newark and North Elizabeth, 

 the writer was compelled to undertake the finding of the source 

 O'f that species. Hitherto, the house mosquito had been con- 

 sidered very local in its distribution but the fact that the elimina- 

 tion of local breeding places did not materially affect this infesta- 

 tion, served to demonstrate that some other factor was con- 

 cerned. 



It was quickly found that efforts to determine relative density 

 through daylight collections were impracticable, and collections 

 made during the early evening were resorted to. This was 

 rendered possible by the use of a large number of inspectors 

 furnished by Union and Essex Counties. 



Collecting the same hour for the same period of time in as 

 nearly similar places as possible, two lines of collections at right 

 angles to each other were run across the infested territory. The 

 result showed a continuous zone of infestation with its greatest 

 density adjacent to Ebling tract of the Essex marsh. Later ex- 

 aminations of the Ebling marsh showed enormously heavy breed- 



