Natural Enemies 185 



State of New Jersey are now being kept entirely 

 free from mosquito laxvse. by small fish. 



In Isthmian practice we examine places for 

 larvae. If fish are able to give us satisfactory 

 results so much the better, if not, then fish must 

 be temporarily sacrificed to prevent human 

 suffering. To profit as much as possible by 

 fish control in general mosquito reduction, the 

 sanitary authorities introduced the Girardinus 

 pcecillodes of Barbadoes into the Isthmus. This 

 is a small fish commonly called a "top min- 

 now" which feeds at the water surface. The 

 female is about an inch and a half long and is a 

 rapid breeder. It was bred successfully in tanks. 

 The young were liberated in the reservoirs, rivers, 

 and ponds and at various parts of Gatun Lake, 

 but not in places where fish were unable to control 

 the situation and larvacide and oil were used. 



Tadpoles were fotmd in cow hoof-prints when 

 water was present, but the Isthmian species did 

 not reduce the larvas in the depressions and obser- 

 vation failed to prove their value as mosquito 

 destroyers. The larvae of dragon flies and water 

 beetles were of great value and were found in 

 places of a temporary character in which fish 

 could not live long and were not found. Probably 

 other aquatic insects were of value. 



