54 



lake was changed from a body of fresh to a body of salt water. Water 

 that is somewhat brackish will support mosquitoes, but water which 

 is purely salt will destroy them. 



^''Practical tiseofjlsh. — The introduction of fish into Ashless breeding 

 places is another matter. It may be undesirable to treat certain 

 breeding" places with kerosene, as, for instance, water which is intended 

 for drinking, although this has been done without harm in tanks 

 where, as is customary, the drinking supply is drawn from the bottom 

 of the tank. An interesting case noted in Insect Life (Vol. IV, 

 p. 223), in which a pair of carp was placed in each of several tanks, 

 in the Riviera, is a case in point. The value of most small fishes for 

 the purpose of destroying mosquito larvtB was well indicated by an 

 experience described to us by Mr. C H. Russell, of Bridgeport, Conn. 

 In this case a very high tide broke away a dike and flooded the salt 

 meadows of Stratford, a small town a few miles from Bridgeport. 

 The receding tide left two small lakes, nearly side b}^ side and of the 

 same size, 1\\ one lake the tide left a dozen or more small fishes, 

 while the other was fishless. An examination by Mr. Russell in the 

 summer of 1801 showed that while the fishless lake contained tens of 

 thousands of mos(juito larvae, that containing the fish had no larvte. 



" The use of carp for this purpose has been mentioned in the preceding 

 paragraph, liut most small fish will answer as well. The writer knows 

 of none that will be better than either of the common little stickle- 

 backs {Gasterosteus aculeatus or Pygosteus pungitius). They are small, 

 but very active and very voracious. Mr. F. W. Urich, of Trinidad, 

 has written us that there is a little cyprinoid common in that island 

 which answers admirably for this purpose. This fish has not been 

 specifically determined, but we hope to make an effort to introduce it 

 into our Southern States, if it proves to be new to our fauna. At Bee- 

 ville, Tex. , a little fish is used for this purpose, which is there called a 

 perch, although we have not been able to find out just what the species 

 is. They soon eat up the mosquito larvffi, however, and in order to 

 keep them alive the people adopt an ingenious flytrap, which they keep 

 in their houses and in which about a quart of flies a day is caught. 

 These flies are then fed to the fish. This makes a little circle which 

 strikes us as particularly ingenious and pleasant. The flytraps catch 

 the flies and rid the house of that pest. The flies are fed to the fish in 

 the water tanks and keep them alive in order that they may feed on 

 the mosquito larvse, thus keeping the houses free of mosquitoes. 



''^Artificial agitation of the water.- — ^Where kerosene is considered 

 objectionable, and where fish can not be readily obtained, there is 

 another course left open. It is ih^ constant artificial agitation of the 

 water, since mosquitoes will oviposit only in still water. At San 

 Diego, Tex., in the summer there are no streams for many miles, but 

 plenty of mosquitoes breed in the water tanks. Some enterprising 



