NATURAL ENEMIES 



461 



found very eflBcient as a destroyer of mosquito larvae and has 

 been extensively introduced into various parts of the tropics 

 from its home in Barbados and other West Indian Islands. 

 Except where other fish are present to prey upon it, this tiny 



Fig. 208. Some good natural enemies of mosquitoes; A, common killifish, 

 Fundulus heteroclitus, of great value in brackish marshes; B, fresh-water killifish, 

 Fundulus diaphanus, valuable in fresh-water streams and ponds, f nat. size. 

 (After Jordan and Evermann.) 



fish usually thrives wherever introduced, and carries with it a 

 noticeable diminution in mosquitoes. Other species of the same 

 family occur in various parts of the world and are almost in- 

 variably deadly enemies of mosquito larvae. 



Other natural enemies of the larvae besides fish might well be 

 encouraged in ponds or reservoirs. The western newt or water- 

 dog, Notophthalmus (or Diemyctylus) torosus, which is abundant all 

 along the Pacific Coast of the United States, has been observed 

 to feed very largely on larvae. In Oregon the author has ob- 

 served grassy pools, which were otherwise ideal breeding places 

 for mosquitoes but which contained numerous water-dogs, ab- 

 solutely free of larvae, whereas other pools not a quarter of a 

 mile distant in which no newts were found were swarming with 

 larvae and pupae. Recent experiments by the author, not yet 

 published, have demonstrated conclusively that this salamander 

 can be utihzed successfully to keep mosquito larvae out of such 

 receptacles as rain barrels, troughs, etc. 



