CHAPTER XIV 



NEW SPECIES THROUGH CHANGED ENVIRONMENT 



One of the interesting points about Leptinotarsa decem- 

 lineata is that they multiply at the rate of two generations 

 a year. This means that a beetle has both children and 

 grandchildren within twelve months. Dr. Tower describes 

 the egg-laying process. It begins in the spring, soon after 

 the beetles crawl out of their underground burrows. 



A convenient leaf is chosen, and the beetle, well laden 

 with her eggs, begins the serious work of laying from thirty 

 to seventy-five of them in close succession. First " she al- 

 lows a drop of yellow, oily fluid to escape " from her body. 

 Upon this the egg is carefully dropped. " The fluid now 

 hardens rapidly and cements the egg in place. One egg hav- 

 ing been deposited, the female moves along a slight distance, 

 and there places another by the side of the first, and so on 

 until there is a row of from five to ten eggs in a nearly straight 

 line across the leaf. A second, third, fourth, and often as 

 many as ten rows are thus laid, each of which is more or less 

 closely placed to the previously laid row, and forms therewith 

 a compact bunch." 



Sometimes, instead of putting all her eggs on the same 

 leaf, the beetle moves from place to place, leaving a few here 

 and a few there, until she has deposited the thirty or seventy- 

 five that are ready to be laid in close succession. Her entire 

 number is about three hundred and seventy-five, but, as we 

 have seen, they have to be laid in separate sets during the 



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