100 ELEMENTS OF GENERAL SCIENCE 



drainage is possible, it is a good method of guarding against 

 the diseases carried by mosquitoes. Another method of de- 

 stroying these insects is to pour kerosene over the water. The 

 oil spreads over the surface of the water and kills the eggs. 

 The larvse and pupae cannot secure air through the surface 

 film of oil, and so die. The adults cannot get to the surface 

 of the water to lay more eggs. The mosquitoes are killed if 

 they get into the kerosene in their attempt to lay eggs on the 



FIG. 55. The yellow-fever mosquito (Stegomyui) 

 Male at left ; female at right. After Howard 



surface of the water. Still another method of getting rid of 

 mosquitoes is to subject them to their natural enemies. Fish 

 eat the larvse, and therefore if the ponds are stocked with 

 fish, the mosquitoes will be less abundant. A very small body 

 of water, as that in an old tin can or in a partially filled horse 

 track, may be ample for the development of a crop of mos- 

 quitoes, and it is necessary to give attention to such places 

 in order to avoid danger. 



114. Different kinds of mosquitoes. There are several dif- 

 ferent kinds of mosquitoes. Only one of these, the genus 

 Anopheles, carries the malarial germ. Our most common 



