48 ANIMAL BIOLOGY 



during the summer it has proven a very efficient remedy 

 and one not very expensive when the area is not too great. 

 Certain fishes, especially sun-fish, stickle back and min- 

 nows devour enormous numbers of mosquito larvae, and 

 the introduction of these fishes into waters where mosqui- 

 toes are in the habit of breeding has often nearly extermi- 

 nated the larvae. Careful attention to rain-water barrels 

 and other stagnant water is also very desirable. In many 

 places, especially where malaria or yellow fever occurs, 

 a vigorous campaign against mosquitoes has greatly re- 



FIG. 39. Aedes fasciata, the yellow- fever mosquito. (After Howard.) 



duced their numbers, and in most situations the trouble 

 and expense of a mosquito crusade would be well repaid 

 by the increased comfort to be enjoyed in the absence of 

 these irritating pests. 



THE FLEAS 



It was formerly customary among entomologists to 

 regard the fleas as Diptera which had lost their wings 

 through disuse owing to their parasitic habits. But 

 however they lost their wings, they are now generally 



