214 THE NEXT GENERATION 



Give two reasons why there was such an extraordinary number 

 of species of snails on Hawaii. When colony after colony had 

 been started in this way, what should we expect to find in regard 

 to their descendants ? What does Dr. Gulick call any separation 

 which prevents one colony from mating with another colony ? 

 What is geographic isolation ? What is food isolation ? What does 

 genuine isolation of this sort result in ? What sets of living crea- 

 tures are controlled by the law of isolation ? 



CHAPTER XIII 



In Kansas what special event marked the year 1862 ? What 

 did one afflicted man write about his experience with potato bugs ? 

 Where did the ancestors of these beetles come from ? When and 

 where did they get their first taste of potatoes ? What years are 

 covered by Dr. Tower's history of the dispersal of Leptinotarsa 

 decemlineata ? What does this record show ? What road did the 

 beetles take in traveling from Illinois to Boston ? Give the records 

 for 1864, 1865, 1868, 1871, 1874, 1875, and 1876. How fast did 

 the beetles travel ? How long did it take them to make the journey ? 

 Why were the European nations anxious ? What weapon did Europe 

 use to save herself ? What was done in Germany and in France ? 

 Describe what happened in 1876. In this journey what did the 

 beetles prove about their own environment? What one thing did 

 they require ? How much time do most potato bugs spend under- 

 ground ? What happens to them in the spring ? Why does the farmer 

 feel discouraged ? What does he do ? Compare the snails of Hawaii 

 with the potato bugs of America : first, the number of species ; 

 second, the kinds of food ; third, the methods of travel ; fourth, 

 the region covered by a single species of snails on Hawaii and by 

 a single species of potato bugs in America. Put together in this 

 way, what do these facts show ? Tell what conditions would have 

 been necessary in order to make many species instead of one 

 species out of the potato bugs of America. 



