CHAP. II The Web of Life 27 



restrial fauna and flora begin. It is a strange and beautiful 

 story, dead shells of the tenderest beauty on the rugged 

 shoulders of the volcano ; corals like meadow flowers 

 on the graveyard of the ooze ; at last plants and trees, 

 the hum of insects and the song of birds, over the coral 

 island. 



4. Nutritive Relations. — What we may call " nutritive 

 chains " connect many forms of hfe — higher animals feed- 

 ing upon lower through long series, the records of which 

 sound like the story of "The House that Jack built." On 

 land and on the shore these series are usually short, for 

 plants are abundant, and the carnivores feed on the 

 vegetarians. In the open sea, where there is less vegeta- 

 tion, and in the great depths, where there is none, carni- 

 vore preys upon carnivore throughout long series — fish feeds 

 upon fish, fish upon crustacean, crustacean upon worm, 

 worm on debris. Disease or disaster in one link affects 

 the whole chain. A parasitic insect, we are told, has killed 

 off the wild horses and cattle in Paraguay, thereby influencing 

 the vegetation, thereby the insects, thereby the birds. Birds 

 of prey and small mammals — so-called "vermin" — are killed 

 off in order to preserve the grouse, yet this interference seems 

 in part to defeat itself by making the survival of weak and 

 diseased birds unnaturally easy, and epidemics of grouse- 

 disease on this account the more prevalent. A craze of vanity 

 or gluttony leads men to slaughter small insect-eating birds, 

 but the punishment falls — unluckily on the wrong shoulders 

 — when the insects which the birds would have kept down 

 increase in unchecked numbers, and destroy the crops of 

 grain and fruit. In a fuel -famine men have sometimes 

 been forced to cut down the woods which clothe the sides 

 of a valley, an action repented of when the rain-storms wash 

 the hills to skeletons, when the valley is flooded and the 

 local climate altered, and when the birds robbed of their 

 shelter leave the district to be ravaged by caterpillar and 

 fly. American entomologists have proved that the ravages 

 of destructive insects may be checked by importing and 

 fostering their natural enemies, and on the other hand, the 

 sparrows which have established themselves in the States 



