1917] Some Recent Advances in Mosquito Work 217 



ent outbreaks within their boundaries. In 1916 it served to 

 demonstrate that the dominant species in Bergen, Essex, 

 Middlesex, Passaic and Union was the fresh-water swamp 

 mosquito {Aedes sylvestris Theob.) and to show that the next 

 problem consisted in the elimination of the breeding places of 

 that species. 



In 1914 Mr. Harold I. Eaton, Chief Inspector of the Atlantic 

 County Commission, undertook the determination of the 

 important factors governing the flight of the white marked salt 

 marsh species {A. sollicitans Wlk.), for the purpose of determin- 

 ing where the limited amount of money available for the use 

 of his commission could be spent with the prospect of affording 

 the people of the county the largest measure of protection. 

 Atlantic County has 50,000 acres of salt marsh and beyond 

 its borders both to the north and the south lie many thousands 

 of acres of undrained marsh. He found that this species took 

 flight on winds of low velocity (10 miles an hour or less), high 

 relative humidity, and high temperature. Under other con- 

 ditions than these, migration proceeds with extreme slowness 

 and covers only short distances. The studies of the writers 

 before and after Mr. Eaton's tests simply serve to confirm and 

 extend the results as stated. 



In 1916, Dr. F. E. Chidester, working at the time under the 

 senior author's direction, determined that, during the mosquito 

 season, the principal factor in the time and geographical dis- 

 tribution of the brown salt marsh mosquito {Aedes contator Coq.) 

 and the white marked salt marsh mosquito {Aedes sollicitans 

 Wlk.) is the degree of salinity of the water to which they are 

 subjected. He found sea water of salinity 6 to 8 per cent, to be 

 favorable to the former and injurious to the latter, while a 

 salinity of 10 to 15 per cent, was favorable to the latter and 

 injurious to the former. 



This discovery fitted well the observed distribution of the 

 two species and seemed to offer an adequate explanation. 

 Be that as it may, the brown salt marsh species is dominant 

 in the spring and early summer throughout the area at a time 

 when the water has been greatly diluted by melting snow and 

 spring rains, and remains so throughout the season along the 

 upper courses of the rivers where the salinity never rises much 

 above the favorable per cent. The white marked salt marsh 



