882 PARKS 



ficially constructed storage reservoirs such as metal, wooden or concrete 

 tanks should be covered with a sixteen-mesh or eighteen-mesh screen. All 

 old cans, buckets or other utensils that may hold water should be buried 

 or burned. Since there will always be water that it is impossible to drain, 

 and since water areas are desirable for many purposes in park development, 

 methods of preventing mosquito breeding in such places must be applied. 

 These consist of killing the mosquito in the wiggletail stage by employing 

 minnows, oiling the surface of the water, or by the use of larvicides. 



Stocking with minnows. For economy and efficiency in mosquito control 

 the possibilities of the minnow cannot be overlooked. One of the varieties 

 of minnows that feeds upon wiggletails is the pot-bellied top minnow, 

 scientifically known as Gambusia Affinis. They multiply very rapidly, giving 

 birth to their young alive in successive broods during warm weather. Their 

 value in mosquito control lies in the fact that they feed voraciously on 

 mosquito wiggletails. The minnows are top feeders and are, therefore, 

 especially efficient in destroying the Anopheles mosquito. However, mos- 

 quitoes of any species have little chance to develop to maturity where this 

 fish is abundant. Vegetation, debris, or other accumulation likely to 

 harbor mosquito larvae along edges of the pool should be cleared so that 

 the fish will find and devour the wiggletails. It is also desirable that the 

 edges of ponds be shallow enough to give the minnows protection against 

 bass and other predacious fish. 



Their usefulness is not confined to streams, ponds and tanks. Two or 

 three fish introduced into a shallow well, underground cistern, watering 

 trough, or rain barrel will live indefinitely, do no harm to the water, and 

 keep it free from mosquito larvae. They will not live in metal overground 

 cisterns. Other fish have also been used in mosquito control, namely, head 

 minnow, small catfish and red horse. The latter two are valuable only in 

 water barrels, wells and cisterns. 



Oiling. Oiling is particularly adapted to the control of small tem- 

 porary pools that cannot be stocked with minnows. The larva is unable 

 to break through the oil film and obtain air when it comes to the surface 

 to breathe. In addition the oil enters the breathing tubes and seems to 

 have a poisonous effect. It is necessary, of course, that a continuous film 

 of oil be kept on the surface of the water, and the frequency of application 

 will vary with the conditions of the weather, the current and so forth. 

 The most economical and effective method of application of oil is by the 

 use of a spray knapsack can, holding about five gallons and carried strapped 

 on the back. A pump is operated with one hand and the nozzle is directed 

 with the other, allowing a thin film of oil to be sprayed to a distance of 

 ten feet. To control running streams drip cans are also used. These con- 



