20 PRINCIPAL HOUSEHOLD INSECTS. 



the mosquito plague could not be greatly diminislied in many, if not 

 most, parts of Baltimore at a very small expense. Usually one well 

 serves two houses, the privies being built in i^airs, so that one treatment 

 would suffice for two dwellings. 



On ponds of any size the quickest and most i)erfect method of form- 

 ing a film of kerosene will be to spray the oil over the surface of the 

 water. 



The remedy which depends upon draining breeding places needs no 

 extended discussion. IS^aturally the draining off of the water of pools 

 will i^revent mosquitoes from breeding there, and the possibility of 

 such draining and the means bj" which it may be done will vary with 

 each individual case. The writer is informed that an elaborate bit of 

 work which has been done at Virginia Beach bears on this method. 

 Behind the hotels at this place, the hotels themselves fronting upon 

 the beach, was a large fresh- water lake, which, with its adjoining 

 swamps, was a source of mosquito supply, and it was further feared 

 that it made the neighborhood malarious. Two canals were cut from 

 the lake to the ocean, and by means of machinery the water of the 

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

 that is somewhat brackish will sui)port mosquitoes, but water which 

 is purely salt will destroy them. 



The introduction of fish into fishless breeding places is another mat- 

 ter. It may be undesirable to treat certain breeding places with kero- 

 sene, as, for instance, water which is intended for drinking, although 

 this has been done without harm in tanks where, as is customary, the 

 drinking sui)ply 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 

 larvcie 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 by side and of the same size. In 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 1891 showed that Avhile the Ashless 

 lake contained tens of thousands of mosquito larv?e, that containing 

 the fish had no larva?. 



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

 paragraph, but 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 pungitms). 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 i)urpose. This fish has not been 

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



