Mosquitoes 



97 



some. Most of these do not fly far. Several of the 

 species that breed in brackish water are great 

 travelers and may fly inland for several miles. 

 Thus the towns situated from one to three or four 

 miles inland from the lower reaches of San Fran- 

 cisco Bay are often annoyed more by the mos- 

 quitoes that breed only in the brackish water on 

 the salt marshes than they are by any of the 

 fresh-water forms (Figs. 86, 87). The worst mos- 

 quito pest along the coast of the eastern United 

 States and for some distance inland is a species 

 that breeds in the salt marshes. 



NATURAL ENEMIES OF MOSQUITOES 



In combating noxious insects we learned long 

 ago that often the most efficient, the easiest and 

 cheapest way is to depend on their natural ene- 

 mies to hold them in check. Under normal or 

 rather natural conditions we find that they are 

 usually kept within reasonable bounds by their 

 natural enemies, but under the artificial conditions 

 brought about by the settling and developing of any 

 district great changes come about. It very often 

 happens that these changes are favorable to the 

 development of the noxious insects and unfavorable 

 to the development of their enemies. 



A striking example and one to the point is af- 



