MAN AND THE WEB OF LIFE 85 



As Locke said : " Things, however absolute and entire 

 they seem in themselves, are but retainers to other parts of 

 nature." 



Fresh-water mussels cannot continue their race unless their 

 young ones sojourn for a while attached to minnows and other 

 fresh-water fishes ; and the continental fish called the bitter- 

 ling (Rhodeus amarus) cannot continue its race unless its young 

 ones sojourn for a while inside the gill-plates of the fresh- water 

 mussel. 



But our subject is not the web of life throughout animate 

 Nature ; we wish to envisage the web of life as it affects man 

 and his interests, or is in turn affected by him and them. 

 Already, however, this is plain, that if animate Nature is in 

 reality a vast interlinked system, the fact must be recognised 

 in all possible detail by every one who would operate on Nature 

 wisely, who would seek to control in any effective way the 

 activities, structure, numbers and distribution of living 

 creatures. If we are to control Nature, we must first know and 

 then respect the intricacy of the web of life. By ignoring or 

 defying it, man has brought much trouble upon the earth. 



1. We may begin with man as a more or less deliberate 

 distributor. It was thoughtlessly but not unconsciously that 

 he introduced rabbits (about 1860) into Australia, with results 

 nothing short of disastrous. It is true that millions are 

 exported as food, but the damage remains. Partly in the hope 

 of checking the elm-tree caterpillars, the European sparrow 

 was introduced into Connecticut. This was done repeatedly. 

 In some measure the sparrow checked the caterpillars, but 

 only to become itself a greater pest, doing much damage to 

 crops and driving away native insectivorous birds. It is also 

 blamed for spreading among poultry certain diseases, such 

 as " blackhead " due to parasitic coccidia. The mongoose 

 introduced into Jamaica to exterminate rats fulfilled its 

 mission, and then proceeded to exterminate poultry and 

 ground birds, besides some useful insectivorous reptiles, some 

 species of which have almost disappeared. Ground lizards of 

 the genera Ameiva, Mabuia and Celestus have become scarce, 

 and some snakes have suffered even more. The reduction 



