June, '14] HEADLEE: ANTI-MOSQUITO WORK IN NEW JERSEY 261 



It was early found that any meadow which was covered at frequent 

 intervals by the tide was free from breeding while any meadow covered 

 only at long intervals or rarely at all reached was sure to breed. Parts 

 of the meadow cut off from tidal covering by dikes or railway grades, 

 garbage or mud fills or parts that are so high lying that the tide only 

 rarely covers them may be expected to breed immense numbers of 

 mosquitoes. 



It is our observation that the frequently submerged meadows 

 are not prevented from breeding so much by the change and move- 

 ment of the water as by the presence of small minnows which are 

 commonly designated as ''killifish." If the extra high tides should 

 fill the pools of the high lying meadows with fish no mosquitoes can 

 be found breeding in them. Of course, if the pools are left long ex- 

 posed without replenishment from either tides or rains, they dry up 

 and the fish die and when rain refills them, breed mosquitoes in enor- 

 mous numbers. 



Salt marsh mosquito breeding occurs not only in the pools, but 

 under favorable conditions may go on in the coarse grasses. This 

 type of breeding becomes possible only when the lower parts of the 

 grass stems are submerged for a period sufficient to permit develop- 

 ment. - Of course, breeding in such spots is prevented by ''killifish" 

 when they happen to be present. 



It seems to the writer that the greatest single factor in determining 

 where mosquito breeding may occur on the salt marsh is the distri- 

 bution of the "killifish." So efficient are they in the destruction of 

 wrigglers that wherever they may be no mosquitoes can breed during 

 the period of their residence. ' Furthermore, they seem possessed of 

 the desire to penetrate the marsh as far as the w^ater will permit and 

 may frequently be seen nosing their way among the grass stems 

 in water two inches deep. 



The 200,000 acres of the Jersey salt marsh present all sorts of 

 breeding conditions. 



That section which hes about New^ark Bay and the lower course 

 of the Hackensack River is made up mainly of the "shut-in" and 

 " high-lying " types of meadow. Breeding originally did occur through- 

 out this area and the swarms of mosquitoes produced inundated the 

 cities on its borders. Of all the municipalities that suffered from that 

 plague, Newark, a city of 350,000 people, was the worst afflicted. 

 When a flight was on, I am told, the electric lights were obscured and 

 public meetings broken up. 



Those parts of these meadows into which sewage is still poured 

 and which are wdthout proper outlets still breed mosquitoes and today 

 form the most serious salt marsh mosquito problem of North Jersey. 



