REPORT ON MOSQUITOES. 93 



It is only in the inaccessible places that the mosquito finds its 

 opportunity. 



"The fact that a species will devour mosquito larvae when in 

 confinement, is not evidence that thev will do so under natural 

 conditions. A fish in an aquarium is restricted in the amount 

 and variety of its food. Its choice is very limited, and it is likely 

 to eat anything offered to it, so that observations made in that 

 way are of doubtful value. 



"I am more and more satisfied that experiments made in tubs 

 are of little value in determining the habits of fishes. It is im- 

 possible to approximate natural conditions in the matter of food. 

 I would much sooner depend on observations made under abso- 

 lutely natural conditions. It is easy enough to jump to conclu- 

 sions from observations made under conditions partly or wholly 

 unnatural; but that is not getting at the exact truth of the 

 question. 



"There are many c[uestions involved in the use of fishes as a 

 factor in the solution of the mosquito problem which can only 

 be determined by experiment. The transfer is easy, but will they 

 remain and multiply? Eel fry were transferred to the great 

 lakes many years ago, and eels are caught there ; but that is no 

 evidence that they multiply. While on the Atlantic Coast the 

 waters abound with young eels, none have been found in the 

 great lakes. On the other hand, about a quarter of a million of 

 shad fry were carried to the Pacific Ocean and planted and shad 

 are now as abundant where there were none before, as they are 

 in the Atlantic. Millions of whitefish fingerlings have been 

 planted in the Potomac River and in certain lakes ; but they have 

 not accepted the conditions offered them or they have been over- 

 come by natural enemies. At all events they disappeared. 



"It is easy to theorize or to jump to conclusions, but in fish cul- 

 ture as in agricultural development there must be rational and 

 patient investigation before there can be really effective work. 



Gregarious Species of Active Habit Occurring in Salt or 

 Brackish JJ'aters. 



"The common tide-water minnows, killies, killifish, mummies, 

 mummichog, etc., are by reason of their enormous numbers un- 

 doubtedly instrumental in preventing mosquitoes from develop- 

 ing in such multitudes as to make human life unendurable along 

 our marshy coasts and lowlands. Breeding principally in the 

 shallow pools left on the mud flats by the receding tides, the 

 young appear in the spring in enormous numbers and remain 

 there until they attain a considerable growth — an inch and a half 

 or two inches — when they begin to run in and out with the tide. 



