158 CIVIC BIOLOGY 



Test the practical value of insect cross-pollination by cover- 

 ing a twig of cherry, plum, or peach with wire gauze or mos- 

 quito netting during bloom. Compare the fruit of this twig 

 with a similar one on the same tree which was not covered. 



Is there any evidence that orchards near apiaries bear better 

 than others? 



What can you learn of the comparative merits of different 

 races of bees in your locality ? 



National problems. In the above list three insects merit 

 special emphasis as presenting civic problems of national im- 

 portance. All are species of almost unthinkable destructive 

 power imported from the Eurasian continent, and until re- 

 cently, at least, without their natural enemies. 



The San Jose scale was imported into the San Jose valley, 

 California, in 1868, and has since spread over almost the entire 

 United States. During this time it has probably killed more 

 fruit trees than all other insect pests combined, and is now the 

 most serious menace to the home fruit garden. Minute as is 

 the insect, one pair may produce *in a season 3,216,080,400. 

 This at once shows how little chance a tree can have and how 

 futile any treatment is which leaves even a few pairs alive. 

 After ten years of experimenting with the various spraying 

 mixtures recommended, the writer is obliged to state as his 

 opinion that nothing has yet been discovered which will ex- 

 terminate the San Jose scale from a tree. Hence it is of the 

 utmost importance for the class to follow all announcements of 

 discoveries as to effective methods of dealing with this insect. 



Make a thorough examination of your home premises and 

 learn the history of the San Jose scale on the place. How 

 much damage has it done from year to year? How much 

 has been expended in fighting it ? What and how many 

 trees have been killed by it ? In connection with the field 

 and laboratory work search for natural enemies, fungus or 

 insect. Make a list of food plants upon which the scale is 



