On the Upland 



On the upland, also, the chief problem is one of drainage. Here 

 we no longer have the tide action to take into consideration but must 

 depend solely on gravity. The elimination of the many large fresh- 

 water swamps is again an engineering problem. Systems must be 

 worked out providing sufficiently rapid outlets of the water to prevent 

 its standing and breeding mosquitoes. Open ditches ordinarily are 



used, although tile 

 drains or filling is. 

 recommended when 

 the expense is not 

 too great. Doing the 

 work with tile, or fill- 

 ing-in gives a more 

 permanent result and 

 does away to a large 

 extent with the ne- 

 cessity for future 

 maintenance. Over- 



Fig. 20— {Above). A 

 Dike on the Essex 

 County Meadows 



Fig. 21— (to the right) 

 A Tide-Gate at Low 

 Tidi in Bergen County 



grown ditches, grassy gutters, etc., should be thoroughly cleaned and 

 the edges cut sharp and clean to prevent mosquitoes from breeding. 

 It is astonishing how often places of this character are absolutel) 

 neglected by the property owners and municipal authorities. Where 

 pools or ponds containing fish have become overgrown, the edges 

 should be thoroughly cleaned to allow the fish a chance to get at the 

 wrigglers. If fish are not present, the pools should be drained 

 or else stocked with fish. In temporary places, and in such perma- 

 nent places as corner catch-basins which cannot be drained or filled, 

 oil or a larvicide is used. Oil forms a film on the water which cuts- 

 off the air from the larva. In trying to get its breathing tube through 

 this oil film, the larva absorbs the oil and is killed. Larvacides per- 

 meate the water and have a poisonous effect on the larvae and pupae. 



House-Mosquito Control 



The methods of control outlined above are applicable where the 

 t>ipiens or Anopheles breed in pools, puddles, or running streams with 



14 



