358 THE WONDER OF LIFE 



idea of subtle inter-relations continually in view. It is 

 at his peril that he ignores the idea. All interferences 

 with the system of Nature — notably exterminations and 

 new introductions — must be sternly criticized. Even the 

 conservation or favouring of one set of organisms by arti- 

 ficial means may be fraught with danger. We shall give 

 a few instances of how the circles intersect. 



The multitudinous economic relations between animals 

 and man have been clearly classified by Sir Ray Lankester 

 in a preface to a British Museum Report on Economic 

 Zoology (1903) :— 



A. Captured or slaughtered for food and other products, 

 e.g. animals of the chase, food-fishes, whales, pearl-oysters. 



B. Bred, or cultivated for food and other products, or 

 for service, e.g. flocks and herds, horses, dogs, poultry, 

 bees, silkworms, leeches. 



C. Promoting operations of civihzed man, but not 

 by being kiUed, captured or trained, e.g. scavengers, 

 hke vultures ; burying beetles ; earthworms, flower- 

 polUnating insects. 



D. Causing bodily injury, death, disease, e.g. lions, 

 wolves, snakes, stinging insects, germ-carriers Uke flies, 

 parasitic worms, etc. 



E. Injuring man's domestic animals, cultivated plants, 

 or wild forms important to him, e.g. as in D, but also 

 injurious insects, pests hke voles. 



F. Injurious to man's worked-up products of art and 

 industry, such as buildings, furniture, books, clothes, 

 food and stores, e.g., white ants, wood-eating larvas, 

 clothes' moths, weevils, ship-worms. 



G. Beneficial in checking the increase of D, E, F, e.g. 

 certain carnivorous and insectivorous birds, reptiles, and 

 amphibians ; some parasitic and predaceous insects. 



