30 LABORATORY LESSONS IN GENERAL SCIENCE 



3. Write briefly the main features of the life history of 

 mosquitoes. What is one way to destroy them in great 

 numbers, and to keep rid of them in an infested region? 

 What more may be necessary? What part is played by 

 one kind of mosquito in the spread of yellow fever ? What 

 must be done in order to prevent the spread of this disease ? 



4. Relate somewhat at length the life history of the 

 common house fly. At what rate do flies multiply under 

 favorable conditions ? What conditions are favorable ? What 



is the procedure in a warfare 

 for their extermination ? 



5. What is the manner of 

 disposal of garbage in your 

 city ? In what respects is there 

 menace to health in such a 

 course ? What better ways are 

 employed by other cities? 



6. In the installation of a 

 sewage system for a town, w r hat 

 must be provided for moving 



FIG. 15. The house fly (magni- , . . . 



fied). Note the hairs on legs the waste material through the 



and body. SCWCrS ? 



7. What is an estimated amount of property losses 

 through the depredations of rats every year? How are 

 buildings made rat proof? Rats are charged with being 

 agents in the spread of the dreaded Asiatic plague. How 

 is this believed to occur? What is done to exterminate 

 them in a city where the plague has obtained a foothold? 



8. Why do we have health ordinances, and health officials ? 

 What are the duties of a Board of Health? Why is there 



