30 ESSENTIALS OF ZOOLOGY 



from the Mediterranean frnit fly. Injurious insects alone cause an 

 annual loss in the United States of more than one and one-half bil- 

 lion dollars ' worth of products if they could be sold at the price the 

 remaining portion brings. With proper knowledge of animal life 

 and application of this knowledge it is likely that at least half of 

 this loss could be prevented. Losses almost as important are caused 

 each year by the parasitism of our domestic animals by bacteria, 

 protozoans, worms, and arthropods. 



Agriculture has benefited greatly from the application of the prin- 

 ciples of heredity to plant and animal breeding. Much fundamental 

 knowledge has come from the extensive studies on the genetics and 

 breeding of the common fruit fly, Drosophila. It produces a new 

 generation about once every nine days. More improvement of strains 

 of animals and plants, too, can be made in one man's lifetime than 

 was previously possible through ages. The United States Department 

 of Agriculture, the Division of Entomology and the United States 

 Fish and Wildlife Service have taken the lead in much of this type 

 of zoology. 



Fisheries and the Application of Zoology 



A very practical and profitable application of zoology has been 

 made in the fishing industry. The annual salmon catch alone on the 

 Pacific coast has been known to be worth $25,000,000. The fishing 

 industry cultures, collects, and markets not only fish of many kinds 

 but also oysters, clams, lobsters, crabs, shrimp, and even sponges. 

 The United States Fish and Wildlife Service does an extensive and re- 

 markable work in the study, propagation, and care of this natural 

 zoological resource. Even with this work and that of all the State 

 Fisheries Departments, the natural fish life does not flourish as it 

 might, had our public more appreciation of conditions necessary for 

 a fish to live. A fish needs suitable water conditions including 

 proper gas content, salt balance, nesting places, vegetation, and free- 

 dom from chemical, soil, or oil pollution. ' - 



The strictly intellectual and cultural endowments which zoology 

 has given man are no less valuable than the tangible gifts. To 

 understand something of the orderly conduct of Nature and to see 

 that her operations are in accord with definite principles, gives one 

 insight to the solution of many of the problems of life. Many of 

 the superstitious dreads of unseen monsters have been eliminated 

 by the knowledge of the fundamental principles of life processes. 



