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ELEMENTARY STUDIES IN INSECT LIFE 



greyhound with weak powers of scent but keen-eyed and 

 fleet-footed. All these have been evolved, under man's 

 direction, from the progeny of the wolf. By artificial 

 selection the many varieties of pigeons, such as the 

 fantail, carriers, and pouters, have been produced from 

 the wild dove of Europe. Every stock-breeder and 

 poultry-fancier is familiar with these principles of arti- 

 ficial selection. Those animals or birds which possess 

 the desired qualities in the highest degree are retained 

 for breeding, while the rougher, smaller and less desir- 

 able stock is marketed. Artificial selection may do in 

 a few generations what natural selection would do even- 

 tually. 



Natural Selection. Let us see if it is possible to find 

 similar selection in the natural course of animal life. 

 We have seen that but a small percentage of insect life 

 reaches maturity, due to the struggle for existence 

 throughout nature. Those who do survive do so by 

 reason of some individual peculiarities. These peculiar- 

 ities seem to be favorable. These favorable peculiarities, 

 characteristic of the survivors, are transmitted to their 

 offspring. Since both parents are liable to possess these 

 peculiarities, the offspring are liable to show the pe- 

 culiarity in a more marked degree. And so it will 

 continue with subsequent generations. Those with 

 favorable variations or peculiarities are liable to live 

 to perpetuate these traits ; these traits tend to become 

 more marked with each generation. The tendency is 

 for those having these favorable traits in a small degree 

 to succumb without leaving progeny. The weaker wasp 

 in its endeavors to capture a spider as provision for 

 its young is more liable to succumb than the stronger. 



